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"(UNIVERSITY OF CALIFORNIA 
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ARMATURE WINDINGS 


DIRECT CURRENT DYNAMOS 


EXTENSION AND APPLICATION 
OF A GENERAL WINDING RULE 


BY 


E. ARNOLD 


ENGINEER, ASSISTANT ay IN ELECTROTECHNICS AND MACHINE DESIGN 
AT THE R1iGA POLYTECHNIC SCHOOL 


TRANSLATED FROM THE ORIGINAL GERMAN BY 


FRANCIS B. DE GRESS, M.E. 


CuH1EF OF TESTING DEPARTMENT, CROCKER-WHEELER COMPANY 





NEW YORK: 
D. VAN NOSTRAND COMPANY 


23 Murray AND 27 WARREN STS. 
1902 


HALLIDIE 


CoPpyRIGHT, 1902, BY 


D. VAN NOSTRAND COMPANY 


_ ‘TYPOGRAPHY BY 
C. J. Peters & Son, 
BOSTON, MASS. 
U.S. A. 


PREFACE. 


WHILE lecturing upon electrotechnics at the Polytechnic in 
Riga, I experienced the difficulty of presenting to the students 
in a brief and simple manner the various methods of winding 
armatures for direct current machines, so as to enable them 
to solve independently any assumed problem in winding. In 
consequence of this, I endeavored to establish rules for the 
various windings, and found that all so called closed-coil wind- 
ings with either a series or parallel arrangement of the in- 
ductors could be embraced under a general rule which applied 
equally well to ring, drum, and disk armatures. The common 
as well as the peculiar properties of the various windings can 
be accurately observed with the aid of this rule. 

The relationship between ring, drum, and disk armature wind- 
ings, is brought into prominence, and the transition from one 
winding to another can be accomplished without difficulty. 
This rule not only embraces all known windings, but accom- 
plishes even more, — a general solution of the winding problem. 
By the aid of this rule,and in conjunction with the various 
methods of connecting inductors treated in the first section, it is 
possible to design other windings. In the later sections I have 
shown several designs for connections, which to my knowledge 
have never been published before. The results which I have 
obtained appear to be of sufficient interest to be made public, 
the more so because even in the best text books on electrotech- 
nics, armature windings, especially those of multipolar machines, 
have been treated somewhat unsatisfactorily. 


(sienED) E. ARNOLD. 
Riga, March 5, 1891. 


ili 


TRANSLATOR’S PREFACE, 





Professor Arnold’s “ Ankerwicklungen,” in which is given 
his general formula for the design of direct current armature 
windings, has been considered of sufficient importance to be 
translated and published in the present form. : 

Many of the designs shown by him are of historic interest 
only, but the principle expressed is fundamental, and of value 
to the enigneer or designer, and no attempt has been made to 
go beyond the subject as treated in his book. 

The translator’s thanks are due to Messrs. A. W. K. Peirce 
and W. I. Crawford, for valuable assistance in preparing the 
work. 


F. B. DE GRESS. 
New York, March 5th, 1902. 


CONTENTS. 


Metuops oF ConnECTING INDUCTORS 


A. CLOSED-coIL WINDINGS... . 


Ring ARMATURE WINDINGS 


1. Breotar Ring ARMATURES . 


MouttieotarR Ring ARMATURES WITH PARALLEL WINDING 


2, 
3. MuttripoLtar Rinc AMATURES WITH SERIES WINDING 
4. 


MuttTireotarR Ring ARMATURES WiTH MIxED WINDINGS . 


Drum WINDINGS 


1. Breotar Drum ARMATURES 


2. Murtieotar Drum ARMATURES WITH PARALLEL WINDING . 


3. Muttiepotar Drum ARMATURES WITH SERIES WINDING 


4. MuLttreotar ARMATURES witH MIxED WINDINGS 


Disk ARMATURE WINDINGS . . . 


Tue Horxinson—MvurirHEAD Disk ARMATURE 


SIEMENS—HALskeE Disk ARMATURE 


. . + 


W. THomson AnD PoLescHKO Disk ARMATURE 


Pacrnotti’s Disk ARMATURE 


Epison’s Disk ARMATURE 


. . . . . . 


Epison’s Murtipotar Disk ARMATURE WITH PARALLEL WIND- 


ING . . . e . . . . . 


APPLICATION OF TITE ANDREWS—PERRY 


PURM Bees eo a ie gtk 
Desroziers’ Disk ARMATURE . 
Fanta’s Disk ARMATURE. 
JEHL AND Rupp Disk ARMATURES 


W. Fritscue’s Disk ARMATURE 


N 


. 


WINDING 


TO Disk ARMA- 


101 


102 
104 
107 
109 
112 


Wace 23 CONTENTS. 


PAGE 

BE OSENSCOIL, 2A INDINOG ee ne Sis Dee IS eee LO 
1. Rirye ARMATURE WINDINGS A hate aie an cee renters) oem Bs, 

2. Drum ARMATURES, THOMSON—HovusTON WINDING ... . 117 

3. Disk ARMATURE WINDINGS, WILDE’s Disk ARMATURE . . 120 
FERRANTI-.THOMGON Disk ARMATURE <9. (s0 20) fe ee we se DI 


PBGEL UA he STOR ei ee ae Re on ee Soe en Bee 





ARMATURE WINDINGS. 





METHODS OF CONNECTING INDUCTORS FOR 
OBTAINING DIRECT CURRENTS. 


Ir an inductor be moved in a magnetic field in such a 
manner as to cut the lines of force, an electromotive force will 
be induced in the inductor. 

If the inductor belongs to a closed circuit, maintains its 
position relative to the direction of the lines of force, and be 
moved with a constant velocity, gcc aie ett 
a constant electromotive force 4 
will be induced, and a current: 2 
of constant strength will be ob- : 
tained. 

The electromotive force is in- 
duced as shown in Fig. 1, per- 
pendicularly to the lines of force 
and perpendicularly to the direc- 
tion of motion. 

Let Fig. 2 represent a mag- Fig. 1. 
netic field produced by two poles of opposite sign; let the 
North pole stand over the paper so that the lines of force pass 
into the paper from the North to the South pole. 

If an inductor be moved in the direction of the double arrow 
through the given field, an electromotive force will be induced 
in it in the direction of the single arrow. 

To produce a closed circuit, it is assumed that the con- 
ductor slides upon two fixed rails, A—B and C— D, whose ends 
are joined by the conductors AmC and BnD. Under these 


1 


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es ee 
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t] 
t 
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1 
~ 
\ t 
re kia be scala ck estas Sr aes art 


Direction of Motion.,.!-” 





2 ARMATURE WINDINGS. 


conditions a current will then flow in the direction shown by 


the arrows. 
A continuous current could only be maintained in this 
_ manner if the field were infinitely large; for as soon as the 


\ oF : 


inductor leaves the magnetic field the induction ceases, and if 
the direction: of motion be reversed, the direction of the flow of 
current is also reversed. 

- A continuous magnetic field, from which a continuous cur- 






























Fig. 2. 











Fig. 3. Fig. 4. 


rent can be obtained, will be made if the field be transferred to 
the surface of a cylinder, and the inductor be moved in a circu- 
lar path as shown by Figs. 3 and 4. 


METHODS OF CONNECTING INDUCTORS. o 


This arrangement involves the principle of a unipolar 
machine. ‘The magnitude of the electromotive force depends 
on the intensity of the magnetic field, on the length of the 
inductor, and on its velocity. The intensity of the field and 
the velocity of the inductor cannot be increased indefinitely ; 
therefore, beyond a certain point an increase of the electro- 
motive force can only be obtained by increasing the length of 
the inductor. | 

But even here certain complications arise. Single straight 
inductors, as ab in Fig. 4, can only be used to obtain small 
E. M. F.’s; higher E. M. F.’s must be obtained by collecting the 
impulses induced in several inductors and putting them in 
series. The uni- 
polar induction, as A 
shown in Figs. 2, 
3, and 4, does not 
permit of series 
connection; for if 





several inductors, 
a—b,. e—d, 2#—f, 
g—h, be connected 
by the cross con- 
nectors, be, de, fg, 
as in Fig. 5, the 
cross connectors 
by their motion through the magnetic field would also have 
E. M. F.’s generated in them, which oppose the E. M. F.’s of the 
inductors; so that after subtracting these opposite E. M. F.’s, 
there would remain that of one inductor, gh; therefore every 
attempt to construct unipolar machines with inductors in 
series, even with the most ingenious connections and devices, 
must fail. aa 

For ‘series grouping, successive poles must be of opposite 
RIOT pe 

If an inductor be moved in a straight line or rotated in a 























& 
Fig. 5. 





+ ARMATURE WINDINGS. 


magnetic field of alternating polarity, at each change of polarity 
a change in the direction of the E.M.F. takes place, and a direct 
current can only be obtained by the use of a commutator. 

The arrangement of these inductors and their connection 
with the commutator must be carried out in such a manner 

































































a | e 
' y Be 4 y Z hoe y 4 & Mk 
ae os vee eee Boar 

c ; ft 





Fig. 6. 


that the E.M.F.’s in all the inductors have the same relative 
direction, and also that the change in the direction of the 
current takes place at the right time. 

In the following figures, the magnetic poles are considered 
as being arranged in a circle at equal distances apart and of 





boas ° 
‘ 


---y 
fy 
‘ 
y 
NY 
= } 
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4 
a 
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ewceneowoeswooaned 





Sew ee ow ee ew ew ee 


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Way cli lew an oh he ws 


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Veen as mee aw awece 


Fig. 7. 


alternate polarity. For convenience in representation, the cir- 
cular path of the inductors is developed into a straight line, and 
the circular arrangement of the poles is likewise represented. 
Some simple ways of connecting several inductors in series are 
thus shown in Figs. 6 and 7. 

The inductors a—b, c—d, e—f, g—h, are connected in 


METHODS OF CONNECTING INDUCTORS. 5) 


such a manner by the inactive connectors l—d, ce—e, f—h 
that their E. M. F.’s, as shown by the arrows, are additive. 

In Fig. 6 the distance between the inductors is equal to 
twice the distance between the poles, while in Fig. 7 it is the 





Fig. 8. 


same as the distance between the poles. The dotted lines show 
the position of the inductors at commutation. The use of con- 
nectors can be overcome by placing the inductors in an oblique 
position, as shown in Fig. 8. With this method of connection, 
it is necessary that the pole pieces be lozenge-shaped, in order 




















SG 


























GWG 








DW 





















































Fig. 9. 


that an inductor should not be in two magnetic fields and 
have opposing E. M. F.’s induced in it. The dotted lines again 
show the position of the inductors at commutation. 

If the inductors a—b, and c—d, in Fig. T, be connected, not 
direct, but as shown in Fig. 9, through bg hi kd so that the 
magnetic field be passed through twice, then the inductors a—b 
and g—h, also e—d and ik, are alternately under induction. 


6 ARMATURE WINDINGS. 


It follows therefore, that the distance between these inductors 
must at least equal the width of the pole; for if both inductors - 
should come within the same magnetic field, the E. M. F.’s in- 
duced in them would be opposed. Fig. 10 agrees with Fig. 9, 
except in the circular form which has been given to the induc- 














tors in place of the rectilinear form heretofore used. The 
inductors in Fig. 10 are in the position of commutation, while 
Fig. 9 shows the point of maximum induction. Figs. 9 and 10 
represent a form of winding, which will be spoken of as “ loop- 
winding.” 

This “loop-winding” may also be obtained by joining 
together inductors that are moving under poles of the same 


Yj Yi YY 
ij Yi Ll O 




















Wry / 





pa 

















Z 





















































CMG 


Flgs.-¥ 1 


sign’ as in Fig. 6, or by connecting, in Fig. 9, h to e direct, 
which gives the arrangement shown in Fig. 11. 

It is evident that we cannot obtain a direct current of a 
constant intensity from the arrangements heretofore shown, 
because the commutation of all the inductors takes place at the 
same moment and when they are all inoperative. 

In order to obtain a direct current of constant intensity, 
a large number of inductors must be used, so arranged in 


METHODS OF CONNECTING INDUCTORS. T 


different parts of the field, that in a certain number of them 
the maximum induction takes place, in others a lesser amount, 
and in some none at all. Then the inductors may be con- 
nected with one another as follows: 

1. In such a manner that they constitute a closed or end- 
less winding, and so that between the points of commutation 
no opposing E. M. F.’s will be induced at any time. The con- 
nection with the exterior circuit must be made in such a 
manner that a reversal of the current in the inductors can 
take place in those only which at the time are not under 
induction. This form of winding will be spoken of as a 
closed-coil winding. : 

2. The inductors may be connected in groups, in which 
all the members of each group are in a magnetic field of the 
same intensity, and only that group which is subject to the 
maximum, or nearly the maximum, induction is connected to 
the exterior circuit, while all the other groups are entirely 
cut out. This form of winding will be called an Open-Coil 
Winding. 

Closed-coil windings will be considered first. 

In Fig. 12 there are two poles, of opposite sign, and the 
inductors are placed at equal distances apart. If we assume 
that the lines of force 
pass from the North to 
the adjacent South 
pole, then the series |' 
winding can be so ar- | | 
ranged that the oppo- | | 
site ends of adjacent | OY Us 
inductors are connected A | = 
together by inactive Fig. 12. 
conductors, i.e., by conductors so arranged as not to cut lines 
of force. These are shown in the figure by dotted lines ; their 
position in space must be imagined to be somewhat as shown 
in elevation by Fig. 13. If the cross connections are drawn 

















8 ARMATURE WINDINGS. 


in for all the inductors, and the direction of the current flowing 
is indicated by arrows, supposing the inductors to move to the 
right, it will be found that they are divided into two groups, 


—B A+ 


VQ AY 








Fig. 13. Fig. 14. 


in which all the E. M. F.’s of positive sign and all of negative 
sign are additive. ~ 

If the scheme of Fig. 12 be arranged in a circle, and A 
be joined to B, an endless spiral is obtained with the permanent 
points of commutation, + and —. 

The reversal of the current does not take place in all the 
inductors at once, but only in those which are at the point of 
































commutation, therefore by using a sufficiently large number 
of inductors the variations in the intensity of the current are 
not noticeable. The current divides itself at the — point into 
two branches which reunite at the + point: this branching of 
the current always takes place in a closed-coil winding, and 
therefore only half of the total number of inductors can be in 


series with each other. 
Fig. 14 shows this branching of the circuit in which 


METHODS OF CONNECTING INDUCTORS. 9 


A—K—B represents the exterior circuit. Fig. 15 represents a 
4-pole arrangement, which is obtained by doubling the arrange- 
ment shown in Fig. 12. Here a double branching of the 
circuit takes place as shown in Fig. 16. 

The inductors are divided into 4 
equal groups, the inductors of each 
group being in series, while the 
groups themselves are in_ parallel. 
Under similar conditions, the E. M. F. 
obtained is equal to that of Fig. 12. 

The inductors can also be con- 
nected in a closed-coil winding, so 
that only a single branching takes 
place; that is, half of. the inductors 
are connected in series whereby double 
the E. M. F. is obtained. This is rep- 
resented in Fig. 17; the joining of the successive inductors 
agrees with the arrangements of Fig. 6, and Fig. 17 may be 
regarded as an extension of Fig. 6. The distance between 
these inductors is either greater or less than the distance be- 





Fig. 16. 

















tween poles, but the sum of them is no longer optional. The 
whole winding deveiops into several angular figures of the 
form 1—6—6, which figure can be considered as the element 
of the winding containing only one inductor subject to induc- 
tion. If this scheme be considered as wound either upon a 
cylinder or disk, so that the inductor AB coincides with A’B’, 


10 | ARMATURE WINDINGS. 


then the number of inductors must be so chosen that the cross 
connections shall always embrace an equal number of divisions, 
and in following out the winding through every inductor the 
last inductor considered will be found connected to the first. 
The inductors must, of course, be taken in their natural succes- 
sion; that is, starting with 6, after going through the whole 
scheme once, we should come to the adjacent inductor 5 on the 
left, or 7 on the right. The proof that this method of winding 
is correct, and gives a single branching, according to Fig. 14, 
can be shown by indicating the direction of the current, and 
following it out in the drawing. Starting from the point of 
commutation 8, and going either in the direction 8, 3, 4, ete., or 
in the direction 8, 3, 8, T, etc., in either case, by following the 
direction of the current through half the inductors, the second 
point of commutation (+) will be reached. At any instant 
the reversal of current takes place only in the two inductors 
which are at the points of commutation, at which time they 
pass from one branch of the circuit to the other. 

A new scheme of the utmost importance in the design of 
multipolar machines may be deduced from Fig. 17, if, instead 
of connecting together those inductors which pass under poles of 
the same sign, as in Fig. 6, we connect those inductors which, 
as in Figs. T and 8, pass under all poles successively. The 
number of inductors and the number of divisions between two 
inductors which are to be connected together must be so chosen, 
that an uninterrupted circuit may be traced out, which, after 
passing through each point of division, returns to the starting- 
point. Figs. 18 and 19 show Figs. 7 and 8 changed to meet 
these conditions. , 

In each element of the winding there are two inductors, 
which are shown by heavy lines in Figs. 18 and 19. If the 
direction of the current be again followed out, there will be 
found only two points where the current apparently runs in 
opposite directions. These are the points at which the current 
for the exterior circuit is collected. We can now solve the 


METHODS OF CONNECTING INDUCTORS. 1 


problem for series winding in general for any number of pairs 
of poles, by multiplying the number of inductors in Figs. 17, 
18, and 19. It will always be found that by this arrangement 



































A f A 
% 2 3 b “ 5 6 : 7 8 g ' 
: g WH, \c 
ARV 
Ae S A KV y 4A GLY 
] 
D LALA ‘ Ys La WY / D 
| 2 3 4 5 6 7 8 9. Sat 
B / Y Y 8 


Fig. 78. 


one-half of the inductors can be connected in series with each 
other, therefore only two points of commutation are required. 
It is evident that the last three schemes can be used in the 
design of direct current windings if every element which 





Fig. 19. 


passes through a magnetic field of alternate sign has induced in 
it E. M. F.’s which are additive. To obtain a complete plan of 
a winding of this character, it is only necessary to join together 
several elements in a closed circuit, and to observe that no vari- 
ation from the assumed form of the element shall take place. 
Many schemes in addition to those shown in Figs. 9, 10, 
and 11 can be devised to meet the conditions outlined above. 


12 ARMATURE WINDINGS. — 














WK 
































LL 














Figs. 20 and 21 show the elements of two windings of this 
character. The element shown in Fig. 20 may be obtained 


from Fig. 9, and that in Fig. 21 by uniting Figs. 6 and 12. 
Fig, 22 is a scheme elaborated from Fig. 9, and Fig. 23 from 
Fig. 11. One element of Fig. 22 contains 4 inductors. 











SS 
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MMXGGGVL 


























A scheme differing radically from those mentioned above is 
shown in Fig. 24. While the windings in Figs. 17, 18, and 19 


METHODS OF CONNECTING INDUCTORS. iG 


always advance through the successive fields in zigzag form ; 
that shown in Fig. 24, alternates back and forth. The in- 
ductor is bent along the broken line 1, 2, 3, 4, 5, 6, 7, making a 
hexagonal or rectangular element, which ends at the adjacent 























Fig. 23. 


points land 7. If new elements of the same shape be added, 
continuing from number 7 on through all the points of division, 
the last element must end at point 1, which gives the scheme 
developed in Fig. 25. 

As may be seen from the figures, each element is subject to 
the action of two poles of opposite sign; by following out the 
direction of the current the points 
of collection (+) and (—) may be 
found. This winding may be spoken 
of as “loop winding,” and that of 


: 1 KY 
Figs. 17, 18 and 19 as “wave wind- Ky 
2 








ing.” + Fig. 22 is a mixed wave and 
loop winding, but as it has the pecu- 
liarities of a wave winding it will 
be classed under that head. 
The characteristic difference be- 7 

tween these windings appears imme- hee 

diately upon comparing schemes like that of Fig. 25 with 
others similar to Fig. 18. While: the wave winding has only 





























1 See W. Fritsche. Die Gleichstrom-Dynamomaschinen. Berlin, 1889. 


14 ARMATURE WINDINGS. 


‘two neutral points independent of the number of magnetic 
fields, the loop winding has as many neutral points as magnetic 
fields. The wave winding in Fig. 25 gives for multipolar 
machines a series winding, while the loop winding gives a mul- 


























Fig. 25. 


tiple winding. Fig. 15 is therefore to be regarded as a loop 
winding (spiral winding). 

Let z be the total number of inductors moved in the field, 
and n the number of poles. Then with the wave winding the 


number of inductors connected in series is equal to ao but with 
sod 


the loop winding it will be equal to =. Under equal conditions 


the E. M. F. in the first case will be- 5 times that of the second. 


In the series winding, the inductors are arranged in two 
groups, corresponding to the single branching of the circuit, 


while in the loop winding it is divided into » groups having 


branches. The inductors of the single groups are in series, 
but the groups themselves are in parallel. As will be shown | 
later, the wave winding may also be used for parallel winding, 
but the loop winding cannot be used for series winding. 

The system of winding given in Fig. 25 can be further 
developed. W. Fritsche suggests that the vertical parts of the 
elements, indicated by the numbers 1, 2, 3, 4, ete., be elimi- 


METHODS OF CONNECTING INDUCTORS. 15 


nated, thereby giving the elements a rhombic forma as shown in 
Fig. 26. 

To avoid generating opposing E. M. F.’s, the pole pieces also 
must be given a rhombic shape. 

The element of a loop winding may be so formed that it 
will lie within the influence of two poles of the same sign 
as shown in Fig 27. The peculiar feature of this scheme is, 
that it is only good for 4, 8, 12, etc., poles, and in this case 


5 





— inductors are joined in series and not — inductors as in the 
n n 


first loop windings considered. In a four pole scheme (n=4), 
there will be but two neutral points, as in the wave winding. 
The cross-connectors in this figure can be so arranged that 

















Fig. 27. , 
they will not cross each other, which gives a wave winding 
similar to that of Fig. 17. 

These general schemes outlined above will now be applied to 
the windings of. armatures for direct current machines. Noth- 
ing further will be said here about open-coil armatures, they 
being treated in a separate chapter. 


\ 
ee 


A. CLOSED-COIL WINDINGS. 


GENERAL FORMULA FOR WINDING DIRECT CURRENT 
ARMATURES. 


FROM an examination of the windings of armatures for 
bipolar and multipolar machines with parallel or series grouping 
applied to ring, drum, or disk armatures, it appears at the 
first glance, that owing to the great variety of them, it would 
be impossible to make a general formula for winding, which 
would cover all these conditions. 

A thorough examination will show that in reality a simple 
formula will cover all windings; that is, for parallel or series 
groupings, for bipolar or multipolar machines, for ring, drum, or 
disk armatures, and one which will show the necessary connec- 
tions of the armature inductors for obtaining the desired results. 
From the observations in the first chapter, it is evident that a 
correct winding will be obtained when those inductors lying at 
the same distance apart in the magnetic field are joined together 
in such a manner that an equal number of inductors or divis- 
ions are always included between two inductors that are con- 
nected together, and after tracing the connections through all 
the inductors, in which, in the separate branchings of the cir- 
cuit the impulses are additive, the last inductor is connected to 
the starting-point. 

The distance between the poles determines which inductors 
are to be connected together. From Figs. 17, 18, and 19, it is 
clear that in following out the schemes, we move alternately 
from the division points on a line AA’, to those on a line BB’. 

If, for example, Fig. 19 be redrawn so that the points on the 

16 


CLOSED—COIL WINDINGS. re 


imaginary lines AA’ and BB’ become two concentric circles of 
which BB’ is the inner, the development of winding becomes 
identical with the following geometrical problem : 

Let the circumferences of two concentric circles be divided into 


ie equal parts. Between the z points of division a line is to be 


2 


drawn so that either one continuous line or several lines result, 
which will be closed on themselves. This will depend on the as- 
sumptions made, and each line in passing once around the circle 
will give a variable number of points of intersection or bending; 
which will also depend on the assumptions made. 

The problem is solved when y, the number of spaces on 
either circumference between successive points of intersection 
on that circumference, satisfies the equation, | 


y = es ae a) where 

k and a are whole numbers. 

6 = the number of inductors lying between two successive 
points of intersection of the broken line on the circle. 

z = sum of the inductors or the sum of the points on both 
circles. 

In Fig. 28, where z = 20, k = 3, a = 1, 6 = 2, we have 


and a broken line of this character is represented. 

Let the division points of the outer circle be numbered suc- 
cessively from 1 to 10; now if y, the number of divisions 
which should lie between two points, equals 3, then 1 should 
be joined with (1 + 8) = 4,4 with (4 +3) =T, ete. On the 
inner circle we observe the same rule. The 20th inductor, Al, 
returns to the starting-point. Since 6 = 2 there are between 
two successive points in the same circle, for instance 1 and 4, 
two inductors, la, and a4. 


18 ARMATURE WINDINGS. 


If 1 be joined direct to 4, then @ will equal 1, and 2z will 
then denote the number of divisions on the outer circle, the 
inner circle being no longer necessary for the construction. — 

Starting at 1, by going once around along the broken line, 
the points a4, d7, g10, are obtained. If zand 6 are given, the 
sum of the broken lines closed on themselves (or loops), or 
the number of points, 
depends on the as- 
sumed values of & 
and a. Returning to 
the winding, let k = 


3 





n 
5 equal half the num- 


ber of poles, and there- 
fore n equals the num- 
ber of poles. Letz = 
number of inductors 
on the circumference 





of the armature; y 
any whole number 
chosen with reference 
8 to the number of 

oe | poles and number of 
inductors; a a constant which when a=1 gives a single 
branching, when a = 2 a double branching, when a = 3 a 
triple branching, etc.; 6 equal the number of inductors in an 
element ( of the winding-z any element. ) 3 

We have then generally, 





Z= v( ty be “) and 


2 (2 
y= 554); 


In regard to the value of z and 6, it should be noticed that if 
the inductor consists of several strands lying alongside of or 
above one another, they are to be considered as a single inductor. 


CLOSED—COIL WINDINGS. 19 


The general rule is: 


The end (beginning) of the xth element shall be joined to the 
beginning (end) of the (x +) element. 


The sum y gives the number of inductors over which it is 
necessary to advance to reach that inductor whose beginning 
shall be joined to the end of the inductor started from. y may 
be called the “spacing” of the winding. 

With the aid of the formula, 


n 
z=bly-_+ta 
(y 2 
the winding of bipolar and multipolar machines can be classified 
as follows : 
1. SERIES WINDING. For this a = 1. In the special case 


when n = 2, parallel and series windings are identical, and the 
winding can be a wave winding as well as a loop winding. 


This is also the case where 5 = 2. (Compare Figs. 44 and 
45.) When 5 > 2a wave winding always results. 


see pon Me 
2. PARALLEL WINDINGS. Windings with 5 branchings 
can be classified : — 7 


A. Parallel winding with loop or spiral winding. In this 
case a multipolar armature is considered as being built up from 
several bipolar armatures and independent of the number of poles ; 
the values n= 2, a = 1 are always substituted in the formula. 


B. Parallel connection in wave winding. Herea=;5- If 


a single winding, closed on itself, is desired, y and ;must be num- 
bers prime to each other. 


3. MixED WINDINGS. Herea >1 and a S53: This case 


results in either several windings closed on themselves with 
special points of collection on the commutator, or a single 
winding closed on itself with a branchings. 

The number of closed windings or elements can be deter- 


20 ARMATURE WINDINGS. 


mined generally, if it is noted that all the elements can be 


joined in a single winding, only when y and 5 are numbers 
Z 

b 

tx p,and y =? xX g, where p and g are two numbers prime 

to each other, ¢ closed windings or 7 independent circuits 

result. 

The total number of branchings still remains equal to a, 
and the points of collection equal to 2a. 

In the following pages we shall consider ring, drum, and 
disk armatures, and prove the correctness of the above formulae. 
We will see at the same time that the formula will always give 
a correct scheme of winding, and that the laying out of a 
scheme for winding by means of the formula is very much 
simplified. 

The methods of representation vary ; in most schemes the 
circular form is retained and the commutator end of the arma- 
ture is shown. ‘The connectors on the front end are shown as 
full lines, those on the back as dotted lines, or they are omitted. 

This method has the advantage over others, that the 
practical development of the winding can be shown, and that 
the transition from ring to drum and disk windings ean be best 
observed. Where it is desirable to show the relationship of 
various windings, Fritsche’s method is used. This gives a 
developed scheme, as shown in the first chapter. _ 


prime to each other. If they have a common factor, as 


RING ARMATURE WINDINGS. 


1. BIPOLAR RING ARMATURES. 


The first winding to be considered will be a simple bipolar 
scheme of the Pacinotti-Gramme type of armature, and in this 
case, with twelve coils. 

All the coils are so connected that they constitute an end- 
less spiral. At each point where two coils are joined, a con- 
nection is made to one of the twelve segments of which the 


CLOSED—COIL WINDINGS. OT; 


commutator is composed. ‘This commutator rotates, of course, 
with the armature. 

With the given position of the poles and the given direction 
of rotation of the armature, a current is induced in the inductors 
whose positive direction is shown by arrows. The stationary 











brushes which carry the current to the exterior circuit, bear on 
the commutator at D, and D,, and a direct current is obtained, 
which, if the number of coils be sufficient, is of a constant 
intensity. . 

A shortcircuit of the armature coils in the neutral zone 
occurs when the brushes are resting upon the two commutator 
segments to which each coil is connected. This shortcircuit 
is followed by a reversal of current in these coils. If the brush 
D, should rest upon the segments a and m, and at the same 
time D, should rest upon f and g, coils 10 and 4, respectively, 


22 ARMATURE WINDINGS. 


are shortcircuited through the brushes. While thus  short- 
circuited they are inactive; but as they pass beyond the point 
of commutation the direction of the current in them is reversed. 

The Gramme winding agrees with the scheme given in Figs. 
12 and 14. In Fig. 80 it is shown again how the current 

branches into the two parallel halves of 
S the armature, D,SD, and D ND., 

This style of armature winding for 
even, sparkless operation requires that 
the two branches of the armature circuit 
| be subjected to an equal induction; 
y 1 therefore both halves must have an equal 
N resistance, an equal length of wire, and 

; must induce equal electromotive forces 
—that is, equal lengths of wire must 
move with equal mean velocities in a field of equal intensity. 

For ring windings, the number of coils which is denoted by 
s, must always equal the number of inductors, z; and the gen- 
eral formula gives 6 = 1, wherea =1,n = 2,z2=s8 = 12, and 
y=s+1 = 138 or 11. 

The beginning of the ath coil is, where y = 11, to be joined 
with the end of the z + 11th, and therefore the beginning of 1 
with the end of 12. When y = 13, it follows that 1 shall be 
joined to 14 (12 + 2), or with No. 2, which agrees with our 
rule. 

When a=2 and y =s— 2=10, coil 1 must be joined with 
1 +10 = 11, and correspondingly, when y = s + 2 = 14, with 
(1 + 14) = 12 4+ 8, or with coil 3. In this manner two inde- 
pendent windings would be obtained, each with one commu- 
tator. ‘To the one would belong coils with odd, to the other 
those with even, numbers. 

The bipolar windings, according: to Wodicka* and Swin- 
burne,+ can be so developed that the number of commutator 
bars should be equal to half the sum of the coils. Fig. 31 











Fig. 30. 


* La Lum, Elec., 1887, Vol. xxv., p. 44. ¢ Ibid., Vol. xxvi., p. 157. 


CLOSED—COIL WINDINGS. Se BB 


shows Wodicka’s scheme worked out for 16 coils. The oppo- 
site coils are so joined that their impulses are additive. 

An element of this winding consists now of two coils. The 
beginning of the eight elements or pairs of coils will be denoted 


















































Yy 
Y Y 
8 
A 
] 
a 
6\~. 
; 2 
7, 
3 
5 ' 
8 
\" 4 
Y YY 
7, 
yl” 
Fig. 31. 


by 1—2—3 ... 8, and the ends, respectively, by 11—2!—3' 
. 8. The general formula is applicable also in this case: 
Here 2 = 2 = 16,8 =2,n=2y=,—-15T. 

The beginning of pair number 1 is to be connected with the 
end of the pair 1 +7=8; that is, with 8', etc. The difference 
between the Gramme winding and that of Wodicka becomes 


24 ARMATURE WINDINGS. 


more noticeable if the Wodicka ring with its winding is devel- 
oped as heretofore. (See Fig. 82.) By comparison with the 


























scheme of Fig. 71, which shows the Hefner-Alteneck drum 
winding, it will be seen that they are identical. 


2. MULTIPOLAR RING ARMATURES WITH PARALLEL 
WINDING. 


The connections of the single coils for parallel winding can 
be carried out in the same manner for multipolar as for bipolar 
armatures. The winding consists. then, independent of the 
number of poles, of a continuous spiral divided up into a num- 
ber of equal sections, at the junctions of which connections are 
made to the commutator. The branchings of the circuit corre- 
spond to Fig. 16. The coils of each branch follow each other 
successively in the ring, and lie in the same magnetic field. 
The number of brushes and the number of circuits is equal to 
the number of poles. Fig. 35 shows this arrangement for a 
4-pole ring armature. Observing that this arrangement agrees 
with the bipolar arrangement of Fig. 29, and that each coil is 
to be regarded as a single element, the general formula applies _ 
as follows: 


Noon ceed 


CLOSED—COIL WINDINGS. 25 
wheren = 2,6=1. Ifa=1ands=16, theny=15. The 
formula requires that the beginning and the end of the adjacent 
coils be joined together. If it be desired to retain 5 branchings 
of the circuit, by inserting the value a = oe another scheme re- 


sults. The coils belonging to the same branching are no longer 
adjacent, but lie at the same time in two or more magnetic 
fields. 

















Whenn = 4, and a = 5 = 2, the number of coils s remaining 
16, then y = 9. Now the end 1’ should be joined to the begin- 
ning of 1 + 9 = 10, etc., as represented by Fig. 34 (compare 
also Figs. 81, 82). 

Developing this circular arrangement, Fig. 35 is obtained, 
in which each coil is represented by a straight line, and may 
be more easily followed. 


26 ARMATURE WINDINGS. 


To obtain the points of commutation, denote the direction of 
the current in the inductors by arrows, and in following these 





out it will be seen that there must be 4 brushes, located at the 


points marked + and —, in order that there shall be no oppos- 
ing E. M. F.’s in the branches. 






























































seabvoe sues Cadiemicsh oan = tmp SPER can ccs ge + CtUS tg olscntw opeermm ce cceee Toe 
2 . a 3 4 = > = A - 
om er = ae .? ae ow? of ae ae -- - a? ae of 
Lor ot # Pe Lae z p as eae Ue* - whe On oe oes on” 
a a * . a 
ae -* - Cee -* > Lad tis se of. oa Bag * dus °° * ant ook 
Lae sk - a? ae o je? LO i? Lot o J Pio d-° oe ae Bt d 
4 r *. 
oc ol oe °° es -* - on -" - -” cod en -* o - 
o” = od - rd - - - - o - a2 a - ‘a ae 
- oF o* od - - - - of - Pid e - o o 5 
a a ar at ol? 4 a md Pa ~ 4 e eo" a7 Pi. 
# -- - - rZ ° o - oe - - - ° - 
Pid aw - - - nae oo?” am - se = £3 o o a ae 
Lew - L-@ st or - Lo -° 2° - Le Le Lm - Lo d- B 
-f o o4 -f - - -1 ar oe 4] 7 - »” - 7 
oa o” - o? - o o* of o* oe of? eo? © a®* o* a” 
oie) of ao”. of on a, ? oe 7 o? ae «? be = m— e 
Z ¢ a - a 4 4 a o o e - 
of - rh o - Pd at - - - o 7 es ae 
-7 as ed eo” on ‘s oo se ia oe - ae Bee =o Pod _ 
a @ on - e - - i - - Le 
a a - a - § L a a 2 4 
ee 24 Pd o” oe” o% Ro cere eth wo a? 7 se uw 
se EF: ey - oo? - - o° * - < =“ - 
- - a?’ - ae; - o Pe La o - Peo - i 
r Pg at tf 4 rr eS ae ea -T ie it 4 34 Let oo , 
e o o - - - - . o - - 
b e at o? L-7 Z ar we ae L- a o*. a. 4-* P 3 an o* ba? 
“| 4 - 
a* 7 o PY - o oe? — of on - - ae - Peas ¥ 
- - - - - - = - - 
Lc Pt ? a . eo e o. - oe Le? oo? L-- Le? ik as 
imr eres ate - wa. 2-900 ee etree eer es coe eer see Ts Ree ceo a ny See 
De Sage eas Tae § hee oo Mae ee i eS Ie 


Fig. 35. 


To observe the shortcircuiting of the coils the positive and 
negative brushes respectively must be considered as conuected 


CLOSED-—COIL WINDINGS. 27 


together by connectors within the commutator, which is shown 
in Fig. 34. At the moment when the coils are in the position 
shown, 15 and 7 are cut out by the negative brushes, and 11 
and 3 by the positive brushes. 

The great number of brushes which is required for the mul- 
tipolar parallel winding can be avoided, if desirable, by the use 





of a winding advanced by Mordey for this purpose. The seg- 
ments of the commutator which are symmetrically disposed 
relative to the fields, are connected together. Then, inde- 
pendent of the number of poles, only two brushes are required, 
as shown in Fig. 36. 

The Mordey winding can be more easily arranged if the con- 
nectors shown in Fig. 36 be joined, as shown in Fig. 37.* The 


* W. Fritsche, Die Gleichstrom-Dynamomaschinen, page 4. 


28 ARMATURE WINDINGS. 


. 2° 
number of segments will then be re and to each segment 5 


connectors are attached. The winding of Wodicka, shown in 
Fig. 31, can also be used for multipolar armatures. Let w+ be 

















SX 


D 





AA 


TT Ls 


Fig. 37. 











the number of winding spaces * on the armature, n the number 
of poles, then those coils which lie between ~+1 winding 
n 


spaces should be connected together as one pair. In Fig. 38, 
s = w=16, n =4, and between each pair of coils, for example, 1 


‘ and 1’, there are — +1= 5, winding spaces. The ends of the 


coils are connected together according to the scheme shown in 
Fig. 33; that is, 1’ with 2, 2’ with 3, etc. In this case 6 = 2, 


* ‘“ Wickungsfelder ’”? = winding spaces, divisions for winding. 


29 








a ace SCC) ay Dyeie ce 



































ae 











‘<S 


CA '> 
ee 














30 ARMATURE WINDINGS. 


a—+1, and the value n=2 must always be substituted in the 
general formula, independent of the number of poles. Fig. 39 
shows the development of this scheme. Wodicka’s method of 
procedure can be expanded by uniting in series 7 coils, if there 











fa a 


Fig. 40. 


be m poles. There must be a segment of the commutator for 
each of these groups, the total number being -. The number 
of winding spaces lying between two coils of a group is again 
- +1. Fig. 40 shows such an arrangement, where s = w = 32, 
and n = 4. Denoting the coils by suecessive numbers, and ad- 


w Me 
vancing each time, — + 1 = 9 winding spaces, the armature 
n 


CLOSED—COIL WINDINGS. 31 


coils to be joined together will be found to be according to the 
following table : — 


Re RR © PE aL ae! © FS: EA emer ai 
Dries SRR Ot Pie ae eo 
sete aie Miah: | a aescetem raul icra ee 
4. Pi: eae meetin ae -y Sage rN ae 
eg Grek Lee yy a Slack ope 
> SY Bano eek + Rese ee Uae | A 
BE ne Be Tg NO ae Ines Te AOL eke hg 
a ae RS 2 Gere re MR cue! Base ae Begeee 2B 
Bates RS aii eae aimee, erie!) 


The formula gives this winding by inserting the values 


b 4 


OXKKKKKXKY 
QQ RR 


2 








NED > 
<s 
=<S 












































Yl | WO YAM 7 
Wie) \\ YG.) | |v | | \4 
ING 
Menno 


Oe 


e f 


Seo 


fi, a, b. S 
h oa b t d 
Fig. 41. 


ONE 
DOS OOR 


Fig. 41, a development of this winding, shows that the scheme 
of connections is identical with that of a wave winding. 
Preserving the same method of winding, it is evident, from 


32 ARMATURE WINDINGS. 


Fig. 41, that the number of commutator segments can be 
doubled by leading to the commutator the connectors coming 
together at a,, 6,, .. h,. 


1 


3. MULTIPOLAR RING ARMATURES WITH SERIES WINDING. 


In the parallel winding of multipolar armatures, there are 
as many branchings in the circuits as poles. In the series 
windings, there being but two branches, only two brushes are 























required. 
wy pe Gy 
JEP lly 
3 5 
. 
vy 2 
PS 
Y 
bls 
9 ) a d 
XF e 
Ly CG 
5 3" 
Z Q 
Fig. 42. 


The scheme for bipolar armatures given in Fig. 30 is there- 
fore also applicable to multipolar armatures with series winding. 

All the coils, starting from the brushes, form two groups in 
which the direction of the current is opposite. Both groups 
must have an equal inductive value. 


CLOSED—COIL WINDINGS. oo 


Under similar conditions, with the same number of turns 
on the armature, the E.M.F. induced by a series winding 
would be 5 times that of a parallel winding, while the current 
would be reduced in the same ratio. 

Series windings should, therefore, be used for high E. M. F.’s, 
or where a low peripheral speed of the armature is desired or 
necessary. As a series winding allows a more simple con- 


1] 





4 



































Wie 


Fig. 43. 

struction of the commutator and brush connections, it is also 
useful in certain cases where a parallel winding might be used. 

A scheme for series winding can be deduced from a parallel 
winding in a very simple manner. In the case of an even 
number of coils, those lying symmetrically and in the same parts. 
of the field are joined so that they may be regarded asa single 
coil, and therefore require a single commutator bar. 


34 ARMATURE WINDINGS. 


As the number of equivalent coils is equal to 5 then the 


8 
number of commutator segments, c, will be ¢ = 2-. 
n 


Fig. 42 shows a scheme where n = 4, s = 12, e = 6. 





Starting from segment a, and regarding the diametrically 
opposite coils 1 and 1’ as a single coil, the end 1’ is joined to the 
segment 6, adjacent to a, and with the beginning of the coil 2 
lying next to 1; 22’ will be the next coil, etc. In this man- 





ner the multipolar scheme is practically reduced to a bipolar 
arrangement and the general formula applies. 

In each coil the direction of the current is reversed four 
times in a revolution, therefore there are 4 x 12 = 48, or 
generally speaking » x s current reversals per revolution. 


When the commutator segments ¢ = 6, and with two 
ns 48 ; 

brushes, each brush shortcircuits rp ect 4 coils. As seen 
c 


CLOSED—COIL WINDINGS. 30 


from the scheme of winding, only two coils are shortcircuited 
at the same time, therefore the scheme cannot be used in this 
form, This difficulty can be overcome by doubling the number 
of commutator bars, as shown in Fig. 43.* To the segments 




















3 
5 : 
2 ¢ 
. 9 


Z 

Y; 

Y 

Y | 7 . 
Y iS e . 


S 





S 10 
4 is 1} 
il 
I ts i v2 
Fig. 46. 


a, 6, ¢, d, e, f, in Fig. 42, must be added a, b,¢, d,e, f, which 
lie diametrically opposite (where n = 4), and to which they are 
joined. 

Generally if the number of coils s is a multiple of - when 
n represents any even number of poles, the number-of commuta- 
tor bars will equal s, and each 5 seoments lying oa degrees 
apart are connected together. Then through each brush = coils 


2 


* La Lumiére Elec., 1887, page 514; The Electrician, 1889, page 139. 


36 ARMATURE WINDINGS. 


will be shortcircuited at the same time. Figs. 44 and 45 show 
the developments of 42 and 43. The connectors or dead 
wires are so drawn in Fig. 44 as to give a wave winding, and 
in Fig. 45 a loop winding. 

In these figures the joining of 6’ with 1 makes the wind- 


ey ee ed atelier Pe ee 
1 c Pa 4 Phe 4 ~ A on p asl vt ont. Z Z, “7 oA 
¢ - Z ¢ ¢ = P hae 2 , y ie ? D 
‘ y 


\ 
‘\ 
N 
\ 
N 
N 
\ 
N 
x 
N 


7 
4 


















































\ Fall eed Cac Mme eg ( on gle et os et aA fy : Ate 

Oe ee Pale ti Fc aa I 
Fig. 47. 

ing unsymmetrical, owing to the even number of coils. As 

6 —1landz =s, if the number of coils be selected according 

to the formula, 


= 





gq ¥ +1, 


the cross connectors will be perfectly symmetrical. 


If 5 be odd, s can still be an even number. In Fig. 46 


8=5 X 7+1=15andy=7. Numbering the coils succes- 


sively, and considering 1, 2, 8, etc., as the beginning and 
1,’ 2,’ 8’, as the ends of the coils, then according to the 
general formula 1’ is to be joined to 14+ 7 = 8, and 8’ with 
8+ 7 =15, ete. 

The commutator bars must be joined together according to 
the rule given; but having an odd number, one segment, 8, 
cannot be so connected. According to the development there 
are always two coils between two segments, and through each 
brush two coils are shortcircuited, except between the seg- 


ments a and b, where there is a single coil. It 5 be odd 


and s even, this unevenness disappears. The developed scheme 


CLOSED—COIL WINDINGS. 37 


is shown in Fig. 47, where a zigzag wave winding with non- 
inductive connectors is obtained. 
From Fig. 46 a new winding can be developed, if, instead of 
n 


joining 2 (or generally 5) coils together without branching off, 


the beginning or ending of each coil be connected to a commu- 
tator segment. That is, if in Fig. 46 segment 6 be connected 
































12 Ws . 
vf, LA 9 2 
2 
| 2 
YU ly 5 
3 
" Te 5 
Ys, ; k rt A \ 
Ys 10 y h * . 
t b 
Y 10 f/e d % A 
Zz 4 
Ui, Ss 5 
Y 9 9 
:;) 6 , 
8 6 5 
8 y 
6, 
7 yk 
“wy ” 
Fig. 48. 


to the coil 1—1’, 1’ be joined not only with 8 but also with 
segment ¢, but 8’ only with segment d, and 15, etc. This wind- 
ing was first used by Andrews.* Perry gave this winding in 
1882.4 S.P. Thompson ¢ is of the opinion that this winding is 
only applicable to an odd number of coils. This view is only 


V7 . . 
correct when 5 18 even. The number of coils must be generally 
* G. Kapp, The Engineer, 60 p. 62, 1885. Kippler, Handbuch, Vol. i., page 533. 
+ S. P. Thompson : Dynamo Electric Machinery, 3d ed., p. 163. 
$ Ibid. 


38 ARMATURE WINDINGS. 


8 =5 yti1. A winding of this character, when the values are 


p=4, s=13, y = 6, c= 13, is given in Fig. 48. Numbering as 
usual, and applying the general formula, it is found that the end 
of the first coil, 1’,is to be joined with the beginning of the y + 1 



































; 4 
i 24 4 
13 | 5 
Y ; 13 oh 5 
716 
12) G 
2 6 
iy 
Tl 7 
| 8 
0: 9 
Fig. 49. 


coil, or of No. 7, etc. By following the direction of the current 
the position of the brushes is found to be 45° apart. When 5 


is odd this winding can be used for an even number of coils. 
In Fig. 49, this is shown, using the values, n = 6, y = 5, s = § 
x 5+1=16. Here the peculiarity exists that the brushes are 
180° apart. If s be odd, which would be the case if y = 8, then 
s=3 x 8 —1= 23, and the position of the brushes would be 
60° apart. 

In Fig. 48, as well as 49, the connections with the commu- 
tator can be made in two planes; that is, in Fig. 48 the connec- 


CLOSED—COIL. WINDINGS. 39 


tions al’, 62’, c3’, are in one plane and aT, 68, and @9, 
in the other, by means of which good insulation is more 
easily maintained. The number of coils which are short- 


circuited by one brush in Figs. 48 and 49 equals 5. In the 


latter figure six coils are cut out of the circuit at the same 











time. Under such conditions, to obtain a steady current and to 
prevent sparking at the commutator, the number of commutator 
bars should be made as large as possible. 

A greater number of commutator bars can be secured, either 
by increasing the number of coils in the armature, or, while still 
conforming to the scheme of Fig. 43, by inserting more seg- 
ments. Using this latter method, and making the number of 








Ax ortHe fF 


Y 
LINIVERSITY 





40 ARMATURE WINDINGS. 


n suey ce ce ee 
segments c=s 5° then each brush will shortcircuit i-~m 1 
eat 


coil. Desroziers * has applied this winding to a disk arma- 


ture shown in Fig. 124. The number of commutator segments 


is generally s > and * segments which are eRe DOUR apart are 
2 n 


joined together, and the number of coils is again s = - ye A. 





a 
LY TAN 
“My a 


Fig. 57. 


Fig. 50 shows a Desroziers winding applied to a ring arma- 
turef where n= 4,8s=9,y=5. Here 1’ is joined tol + 5 = 6, 
and 6’ with 6’ + 5= 9 + 2, therefore with number 2. 

The extra bars necessary are shown in section; omitting 
these, the winding of Andrews and Perry results. If it be desira- 
ble, the number of collector bars can be decreased by applying 
the scheme of the drum winding to the ring. If the number of 


* Electrotech. Zeitschr., Vol. x., p. 200, 1889. 
+ Rechniewski, La Lum. Elec., Vol. xxiv., p. 516, 1887. 


CLOSED-COIL WINDINGS. AL 


coils be s =5 (5 yt 1), then the winding can be so arranged 

thate =—-. F ig. 51 shows this winding, using the values 
v7) > 

n=4,s=2x 18,c=13,y=6. The pairs of coils belonging 

together are shown by the same numbers, and the connections 

are carried out according to the general formula. 





Instead of joining in pairs coils lying in magnetic fields of 
opposite polarity, as shown in Fig. 51, adjacent coils may be so 


joined. ‘The number of segments would then be generally 5? 
assuming 6 = 2 and s = 2 é yt 1), In Fig. 52 the values 


assumed are n = 4, s = 9, y = 5, and the beginning and ends 
of pairs of coils are indicated by the same numbers. 

To obtain a series winding according to the general formula 1’ 
is joined with 6, and 6’ with 2, etc., and to each junction a com- 
mutator bar is connected. If the points a, 0, ¢, d, e,f, g, h, i on the 


492 ARMATURE WINDINGS. 


cross connectors be connected to the commutator, the resultant 
winding will be the same as that given by Andrews and Perry. 
This winding can also be carried out if the number of coils be 
a multiple of the number of poles ; but the winding will no longer 
be symmetrical, as in Fig. 52, but unsymmetrical, as in Fig. 53. 














me 
The number of segments becomes c¢ =a! +1. As there are 12 


coils altogether, 10 of which are joined to form 5 pairs, the two 
remaining must be connected independently so that 7 collector 
bars are necessary; therefore y=4. The number of coils that are 


ers Sar sn Nn 
shortcireuited in Fig. 52 by one brush, is equal to 5-=— = 4. 
20. a8 
2 


This number can be decreased for any number of poles, n to 2, 
by using the methods in Figs. 43 and 50, and by making the 


Si 
number of. commutator bars ¢ equal to rie A scheme result- 


CLOSED—COIL WINDINGS. 43 




















Fig. 54. 


ing from this arrangement is shown in Fig. 54.* An element 
of this winding contains two inductors, so that if 6 = 2, 
y = : (5 - 1) or y=3(5- 1) — 4,and 1 is joined to 5’ or 1’ to 
5. Omitting the segments shown in cross-section, the scheme 
shown in Fig. 52 again results. 

Alioth & Co. use this scheme for drum windings, and Jehl and 
Rupp use it for disk armatures. (Compare Figs. 91 and 131.) 

3 a. s’ G’ bs gf 


i 





















































* La Lum. Elect., Vol. xxiv., p. 515. 


44 ARMATURE WINDINGS. 


Fig. 55 is the development of Fig. 54, and shows a wave 
winding, with alternate long and short waves. 














Fig. 56. 
4, MULTIPOLAR RING ARMATURES WITH MIXED WINDINGS. 
The term “mixed windings” is applied to those which 


ay ae 
result when a has the value a> 1 and ~“in the general form- 


ula s=b= (ya). 

The possible number of these windings, if developed for 
parallel or multiple windings, would be large. It is not the 
intention to investigate here their usefulness or significance, 
but to present a few typical cases. In Fig. 56 the values n—6, 
b=1,.a=2, y=4, are assumed, then s=14, and the scheme gives 
two independent series windings which require the brush po- 
sitions B,, B, B,, B, If the number of coils be odd, for in- 


CLOSED—COIL WINDINGS. 45 


stance, y=5 and s=17,a simple winding closed on itself would 
‘result, requiring 4 brushes. Fig. 57 represents this case where 
n= 8, a=2, 6=1, y=5, s=22. All the coils are joined into a 
closed spiral. If the assumption is made that n=6, a=4, 
6=1, y=10, s=34, the interesting winding shown in Fig. 58 


WLM 


Fig. 57. 





results. This arrangement has two independent windings for 
each set of 17 coils, with the brush positions a, ¢, e, g and 4, d, 
Ff, h, which fall together in pairs. So that although the coils are 
joined in eight parallel groups, only four brushes of double 
width are required, therefore, for a six-pole machine, an eight- 
branch-winding with four sets of brushes results. Fig. 59 
shows the arrangement for a six-pole machine if the number of 
coils is odd, which would be the case if y = 9,a = 4, s = 81. 

All the coils belong to one winding. Of the eight brush 
positions in two places two of them fall on adjacent commu- 
tator bars, so that six brushes are sufficient. 


46 ARMATURE WINDINGS. 


! 


































































































34 i 
3 ’ : 3 
31 4 
>. 39 5 
2 G 
u 7 
2 ; 8 
26 = 9 
2 if 
23 12 
22 13 
a 
al 14 
20 | 
Fig. 58. 
| ee 
3 
2 
yz 
2 
§ 
6 
9 
] = 7 
23 
“, wd 8 
2 
9 
9) 
10 
20 
" 
19 (9 
18 
6 fis \4 
| 
| 
Fig. 59. 


~ 


CLOSED—COIL WINDINGS. 47 


DRUM WINDINGS. 


1. BIPOLAR DRUM ARMATURES. 


From the Siemens double-7' inductor and two-part commu- 
tator, Von Hefner Alteneck, in 1872, developed an armature 
winding which for direct-current use was fully equal to the 
ring winding of Paccinotti. 














—¥".4 tik 
ood as rd Mane, 
‘ 1 3: 
7“ i Se 
— ES cea 4 . me xs 
Seana a ee dees & 3 
rai ea Se », 
7 » A ve “ 
IN ‘ > a : Ne 
6 VY : 4 : 
3 
] N 
Fig. 60. 


Von Hefner Alteneck wound the coils upon a drum parallel 
to its axis, so that by rotating the drum in a magnetic field the 
two sides of a coil on the surface of the drum were subject to 
induction. In this form of winding, it is evident that the num- 
ber of inductors. z is equal to double the number of coils 8S. 
There are as many commutator segments as. coils, and each 
segment is connected with two coils in such a manner that the 


48 ARMATURE WINDINGS. 


whole forms a closed winding which is divided in two parallel 
branches between the brushes. 

For simplicity in representing this form of winding, a 
scheme employing eight coils, and therefore eight commutator 
bars, a, b, e, d, e, f, g, h, will be selected as in Fig. 60, which 
represents this armature viewed from the commutator end. The 
inductors around the circumference of the drum are therefore 





xs 








AC 
ia 
3 : ea d M, 
WK SX 
: ‘ B 


we r 1 3 





wN 

Fig. 67. 
represented by points, while the connectors across the back are 
shown by dotted lines, or entirely omitted. Assuming that the 
inductors lie at equal distances apart, as each element has two 
inductors, 16 winding spaces are required. The circumference 
of the cylinder is therefore divided into 16 equal parts, and 
alternate divisions are numbered 12... 8. Space number 5 
is diametrically opposite to space number 1. In order that the 
second inductor 1’ of the coil 1 1’ shall not fall upon space 


CLOSED—COIL WINDINGS. 49 


number 5, it must be carried either to the right or to the left 
of that space. In Fig. 60, 1’ lies to the right of 5. Start- 
ing from 1’ and following out the numbering, clockwise, in 
the same direction and manner as before, the remaining divis- 
ions will be numbered successively 2’ 3’. . . 8’.. The numbers 
1 to 8 will represent the beginnings, and 1’ to 8’ the ends of 
the corresponding coils. For instance, to obtain the coil 1 1’ 





starting at 1, the conductor is carried along the surface of 
the cylinder to the rear end, then at right angles along the 
dotted line 1’ 1 across the rear end, and brought to the front 
again, then along 1 1’ to the point of departure. This is 
repeated until the coil has the desired number of turns. The 
end of the last turn is not carried back to 1, but is left of 
sufficient length at 1’ to be connected to its segment of the 
commutator. 


50 ARMATURE WINDINGS. 


_ In this manner 16 sections, 1 to 8, 1’ to 8’, are obtained, 
whose connections to the commutator are absolutely determined 
by the general formula. Observing the rule that every cross 
connector must be connected to a commutator segment, it is 





evident that the number of commutator segments must be 
equal to the number of coils or sections. 

It is immaterial from which section the start is made, that 
is, which commutator segment is connected with 1; but it is 
necessary that the remaining sections be connected in succession, 
advancing either to the right or to the left. The first is spoken 
of as a clockwise, the latter is an anti-clockwise direction of 
winding.* Fig. 60 represents the development of a Von Hefner 
Alteneck winding with a clockwise, and Fig. 61 with an anti- 
clockwise advance. In both figures, 6 = 2,a=1, n = 2, 


* Compare Dr. A. Von Waltenhofen, Zeitschrift fiir Electrotech., 1887, p. 316. 


CLOSED—COIL WINDINGS. 51 


2 
z2=2s8=16,y= : (, —1)=f7. Therefore the beginning of 
any coil 2 is to be joined to the end of the 2th + 7th coil; 
that is, 1 with 8, ete. 
Following out the direction of the current, which is shown 
by. arrows, the position of the brushes can be easily determined. 





It will be observed that on rotating the armature clockwise the 
negative brush will be to the right of the line joining the north 
with the south pole if the advance is also clockwise, and to the 
left if the advance be anti-clockwise. Both brushes are upon 
the diameter mm,, which, if there be a large number of coils, is 
nearly perpendicular to the line joining the north to the south 
pole. In Figs. 60 and 61, which have only eight coils, the 
brushes are noticeably advanced in the direction of the wind- 
ing, so that the angle mOS departs considerably from 90°. 


52 ARMATURE WINDINGS. 


Starting from the negative brush the current divides into the 
two branches, : 


Bd44 e556 6 gT TB, and 
bas Ben Zo Las She, 


It will be observed that two adjacent coils are shortcircuited 
as soon as they lie in a plane perpendicular to the pole line WV.S., 
for example, 3 38’ and 7 7’, Figs. 60 and 61. 























Fig. 65. 


The only distinction between the Edison winding and that 
of Von Hefner Alteneck is, that the connections with the com- 
mutator in the former case are so carried out that the position 
of the brushes coincides with the pole line V.S. 

Figs. 62 and 63 show two schemes with this change, and 
with clockwise and anti-clockwise advance. The change con- 
sists in turning the commutator and connections through the 
angle m’ OS (Fig. 61), in the direction of the winding. The 


CLOSED—COIL WINDINGS. 53 


position of the negative brush becomes independent of the 
direction of the winding. Its change of position with the posi- 
tive brush depends only on the change of direction of rotation. 
As already stated, in the old Edison and Von Hefner Alteneck 
method of winding, two adjacent coils are shortcircuited at the 
same time. With high potentials it is difficult to maintain a 
good insulation between the coils, and Bréguet found it advan- 








tageous to develop the winding in such a manner as to prevent 
the shortcircuiting of two adjacent coils. Figs. 64 and 65 show 
this method for the same number of sections. The difference 
between this and the previous schemes is that inductor 1’ of 
the section 1 1’, does not lie immediately to the right or to the 
left of number 5, but, as in Fig. 64, is carried to the left of 6, 
or as in Fig. 65 to the right of number 4. The two coils 
which are shortcircuited in this case, would be 11’ and 55’, 


54 ARMATURE WINDINGS. 


or 33’ and 77’, each pair being separated by two winding 
spaces. 7 

The drum windings which have been so far considered have 
had an even number of sections, and further the winding spaces 
of all the coils have been side by side upon the surface of the 
drum. To accomplish this, it has been necessary to make the 
rear connection follow a chord. 








5 
N 
Fig. 67. 


They can be wound along a diameter providing : 

1. An uneven number of coils be employed, and 

2. Superimposed winding spaces be used with an even 
number of coils. 

Fig. 66 represents the winding with an uneven number of 
sections, in this case s = 9. In the position shown, while the 
negative brush lies upon the segment d, the positive brush is 
shortcircuiting coil 8 8’, and lies upon two segments h and 2. 


CLOSED—COIL WINDINGS. 55 


Two coils are never shortcircuited at the same time, and there- 
fore, as in the Bréguet winding, two adjacent coils are never 
shortcircuited. The circuit through the armature.is through 
the remaining eight coils in the two directions ; 

d44 e5 5S fOOGgTTh, 

GSS ¢2 261 Lav. 94, 
each having equal lengths of conductor. As there is not 
always room enough to place the winding spaces side by side, 





Fig. 68. 


it is at times necessary to superimpose the winding spaces of 
two adjacent coils. Fig. 67 shows this arrangement for a Von 
Hefner Alteneck winding, advancing clockwise, and Fig. 68 
for an Edison winding, advancing anti-clockwise. In both these 
schemes the number of coils is eight, and the number of wind- 
ing spaces also eight. If the coilsa1 1’,622),¢33,d44e 


56 ARMATURE WINDINGS. 


be put on first, the eight winding spaces will be occupied and 
four commutator segments, a, 6, ¢, d, used. In order to use the 
other four commutator segments e, f, g, h, the remaining four 
coils may be wound over those already put on; that is, 5 5’ over 
1 1,’ 6 6’ over 2 2’, 7 T’ over 3 3’, 8 8’ over 4 4’, and 8 returns 
to the starting-point. The two coils 3 3’ and 7 7’ which lie 











upon a diameter perpendicwar to the diameter V. S., and 
therefore in the neutral zone, are the coils which are short- 
circuited by the brushes, thus determining their position. 

The connections of the coils and the position of the brushes 
follow the rules previously given. Although the schemes 
described are frequently employed, they have a slight disadvan- 
tage in that the two parallel circuits of the armature have not 
an equal inductive value, which increases the tendency to spark 


CLOSED—COIL WINDINGS. Si 


- at the commutator. To balance the two circuits of an armature 
it is necessary that they be of equal resistance, which implies 
an equal length of conductor in each, and that the inductors of 
each half have an equal mean velocity. In the schemes where 
the sections are wound alongside each other these conditions 
are obtained, neglecting the small mechanical difficulties in 








N 
Fig. 70. 


crossing at the ends, but not in the schemes with coils super- 
imposed in pairs. If the armature in Figs. 67 and 68 be 
turned through an angle so that segments a and e are under 
the brushes, the two branches of the armature are as fol- 
lows: a@11', 622,¢33),d44e,a8 8, AT 7, 96 6,f 5’ de. 
One consists of all the interior, the other of all the exterior 
coils. The induction in each half, and also the resistance, is 
equal only at that time when the brushes lie upon ¢ and g, 


ARMATURE WINDINGS. 


58 


N 





; SS 


' 
ft 
. 





DC. 























— 





r 









.,.\)WL) 
KJ 


OS 


BK VY 











WG 


each half two exterior and two interior 


as there are then in 


coils. 


this inequality in the two branches of 


The evils arising from 


CLOSED—COIL WINDINGS. og 


the armature can be easily overcome by properly connecting the 
coils. An absolute balance in the induction for every part of 
the revolution can only be obtained when half the sum of the 
coils is odd. Fig. 69 shows such an arrangement having 14 
coils. 


Yy WY. 














Fig. 73. 


In laying out this diagram the winding spaces are numbered 
1, 2, 8, etc., alternating between the exterior and interior circle, 
and the coils are connected according to the general formula. 
The successive sections will then lie alternately upon the outer 
and inner cylinder, and the halves will balance. 

If half the number of coils be even, as in Fig. 70, the 
scheme no longer gives a symmetrical winding, and the num- 
bers do not alternate successively from the outer to the inner 
cylinder, but in one place two winding spaces on the outer and 


60 ARMATURE WINDINGS. 


two on the inner cylinder are adjacent. In Fig. 70, f 6 6’ 
g7 TU h,and 6 1’ 1412’ 12 m, are the coils referred to. This 
variation of the Siemens winding, which was proposed by 
Weston, has the disadvantage that the difference of potential 
between the superimposed coils is as great as that between the 
adjacent coils of the Siemens scheme. ‘The use of heavier insu- 


Vs yy 


It 




















lation, which higher differences of potential necessitate, in- 
creases in the Weston armature the depth of the winding and 
consequently the distance of the core from the pole pieces. 
Fritschie’s method of representation is especially applicable 
to drum armatures. The development of one of the given 
schemes with eight sections or 16 inductors is shown in Figs. 


Ticor tz, 
The poles are shown in cross-section, and the connectors are 


CLOSED—COIL WINDINGS. 61 


indicated by the broken lines as heretofore. The point of 
commutation can be obtained by following the direction of the 
currents as indicated by the arrow points. The cross connec- 
tions are such that in Fig. 71 a loop winding results, while in 
Fig. 72 they give a wave winding. 














— + = 
ny) | Vy ( oe ) 
YG \ GPA \\OGGG |.V GGG |. 
py, |" CO UYU) \0 AHF Uj 
UT ae 
baG Y j ¢ YK 


<< O.W 


MANY 


This method of representation led Fritschie to another style 
of drum winding. Consider the scheme of either Fig. 71 or 72 
in unchanged form as being wrapped around a cylinder, then 
the faces of the cylinder remain free from cross-connectors, the 
whole winding being carried on the surface of the cylinder. 
A peculiar application of the Von Hefner Alteneck winding 
is shown in the armature of the Immisch motor, Fig. 73.* 
8 
2 
commutators are so placed that the middle of a segment of one 
is opposite the space between two segments of the other. 
Each brush consists of two parts joined together and resting 


This has two commutators, each with — segments. These 


* La Lum. Electr. 1887, vol. 24, p. 261; Elektrotechn. Zeitschr., 1887, p. 531. 


62 ARMATURE WINDINGS. 


upon both commutators. In Fig. 73 these commutators are 
represented as concentric circles. ‘The circuit is the same as 
ina Von Hefner Alteneck drum, and both windings would be 
identical if the segments of one commutator (in the Immisch 
armature) were inserted between those of the other, for ex- 
ample, ¢ between a and 6. The double commutator gives the 
same result as the ordinary form, except that the coils remain 
shortcircuited longer. 





2. MULTIPOLAR DRUM ARMATURES WITH PARALLEL 
WINDING. 


In designing an armature winding of this character the 
method of procedure is the same as before. The core is 
divided into the desired number of winding spaces, the ends of 


CLOSED—COIL WINDINGS. 63 


the coils numbered 1, 2, 3, etc., and 1’, 2’, 3’, etc., and the gen- 
eral formula applied. If the parallel branchings of the arma- 
ture are to have equal lengths of conductor it is necessary that 
the number of coils be made a multiple of half the number of 


poles (5) ; 


n 
If = 
co 

if 5 be odd, then the number of coils may be either odd or 


be even, then the number of coils must be even, but 


even. If the number of coils be a multiple of n, then n coils 
will be shortcircuited at the same moment by the v brushes ; 


but if s be only a multiple of a then theoretically, only ‘ coils 


will be shortcireuited, but practically n coils will still be 











bE BR 
1g PhP oy 
2 3 
17 Wi 
| 7 ‘ 4 
ae, K\2 a 
18 r ss 5 
15, / J 
Fe : 
17 aS 4, 6 
14 4 
\ 
16 \ 7 
4/e: 
5 
x / 
8 
1S\ * / 
o 19's re a 
’ 
aN Pf ge 
1] ; 
13 wos sabes B -=r—"10 
fae ere 8 


64 ARMATURE WINDINGS. 


- shortcircuited at the same time, owing to the width of the 
brushes. 

This may be observed in Fig. 74, where n = 4, 2 = 2s = 24. 

ve 

In the general formula, y = = = 1) , the values a = 1,n = 2, 
are substituted to obtain a parallel winding, and y = . —1l= 
S—1=11. Therefore 1’ is to be joined to 1 + 11 = 12, and 
to one commutator bar, etc. If this be reversed, and 1 be 




















Fig. 78. 


joined to 12’, an equally correct scheme will result, the only 
difference being that the positive and negative brushes change 
places. In Fig. 74, 4 coils are simultaneously shortcircuited, 
for example, 3 3’,6 6’,9 9’,12 12’. Fig. 75 represents the 
developed. scheme of a multipolar loop winding. 

If the position of one inductor of a coil, e.g., 1, be assumed, 


CGLOSED—COIL WINDINGS. 65 


then the position occupied by the second inductor 1’ will be 
the same as that in a bipolar armature. In Fig. 74, 1’ can lie 
as well to the right as to the left of 4, or following Bréguet 
two additional winding spaces can be inserted between 4 and 1’, 
1’ may also be wound over 3 or 4. The conditions which govern 
the number of coils in this case are similar to those of a bipolar 


+ ~ + - 


—_— 
~ 


SEQ MAA 


<REN 
































SSS aay 





armature with an odd number of coils. This number must be 
a multiple of = but not of n, and only 5 coils are simultane- 


ously shortcircuited, as can be seen from Fig. 76. 
If the coils are wound side by side, each coil can be so 
placed that its inductors lie symmetrically in the field; that is, 


1 
each coil embraces the ja part of the circumference of the 


drum. This angle of embrasure can be greater, or preferably, 
smaller; for the smaller the angle the fewer the number of 
crossings of the coils, but at the same time the surface 
embraced by each coil is so much less. 


66 ARMATURE WINDINGS. 


This can be observed in Fig. 77 with n = 6, and an odd 
number of coils, s = 21, y=s—1= 20. In the position 
shown in Fig. 76, coils 10 10’, and 3 3’, are shortcircuited, and 
in Fig. 77. coils 7 7’, 1414’, 21 21’, are likewise shortcircuited. 
On rotating the armature to the right, the next coils to be 
shortcircuited are: in Fig. 76, 13 13’, and 6 6’, and in Fig. 77, 





Fig. 80. 


3 8’, 10.10’, 17 17’... The number of winding spaces in Figs. 
74 and 76, which lie between the inductors of two coils, for 
example, 1 1’, are counted in the direction of the numbering ; 
for example, 1’ lies to the right of 1. If 1 be considered as 
lying the same number of winding spaces to the left as it was 
previously to the right, retaining the same system of numbering, 
a scheme will be obtained which has been used by Thury for 
multipolar drum winding. In this scheme of Thury’s, which 


CLOSED—COIL WINDINGS. 67 


is shown in Figs. 78 and 79, there are not so many crossings 
of coils, having a considerable difference of potential between 
them, as in the drum windings previously given. This can be 
observed by comparing Fig. 79 with Fig. 75. 


2 
If a be given the value “in the general formula, y = al Sa “), 
another scheme of parallel winding (wave winding) can be 


f e a b > 9 d 



































YYGGGZ GG 7 
447077 WW \ YAW 
is AGA VIVA 46) |r VA INVALASIAA hs 
KWOOMA | VAN AANA A Z 
IWABVACLA's SAY, ZVA3 | \s Wy” WA 
Y) 
ZZ | ZG4¢ Wl, GAG Li Z 


Fig. 81. 
obtained. The scheme shown in Fig. 80 is obtained by assum- 


1 /32 
ing the values n = 42-28 —82y 5 (> — 2) =7. 


All the coils are joined together in a single closed winding. 
This winding is peculiar in the fact that the coils are short- 
circuited by two brushes, either the two positive or the two 
negative; for example, if the two brushes lie upon the seg- 
ments ab and ed, then 15 15’ and 7 T’ are shortcircuited, and 
when they lie upon ef and gh, then 11 11’ and 3 3’ are short- 
circuited. It is understood that the brushes of the same sign 
are connected together, or else that the corresponding segments 
are joined as in a Mordey winding. Comparison of the scheme 
of Fig. 81 with that given in Fig. 41, shows that both windings 
are of the same character. 


68 ARMATURE WINDINGS. 


If y and s have a common factor, then this winding scheme 
no longer gives a single circuit, but several circuits closed on 
s—2 





themselves. Ifn=4,8s=14,y =2 — 6, two inter- 


laced windings would result, each being a series winding with 
two brushes. In Fig. 82 the full lines represent one of these 





windings, the dotted lines the other, and the coils 13 13’, and 
6 6’ are shortcircuited. The construction of machines using 
multipolar windings with parallel branching requires great care, 
not only with regard to the symmetry of the winding itself, 
but also with regard to the intensity of the magnetic field. 
The effect of different intensities in the several fields are over- 
come in the winding schemes shown in Figs. 81, 82, as the 


CLOSED—COIL WINDINGS. 69 


coils lying between two brushes are distributed through all the 
magnet fields. 

If the coils be superimposed as assumed in Fig. 83, a sym- 
metrical arrangement of the same can be attained by connecting 
alternate inside and outside coils with one another. (Compare 
with Fig. 69.) 





Fig. 83. 


In this figure, with the position given, the four branchings 
of the circuit are : 


e; 14°14, d, 15’ 15, e, 16°16, 5, 1° 4, a; 
#43 18°, 7; 12 12, 9, 41 TP; h 10, 4, 
ey Goat i, 6, 8 8, bo Fe, 

C4 OD af at £5 Gi O85 hy 2258: 


To each of these branchings belong two inside and two 
outside coils. The Mordey winding for ring armatures, as 


70 ARMATURE WINDINGS. 


shown in Figs. 36 and 387, can be carried out in the same 
manner for drum armatures. __ 

A four-pole drum armature of Alioth & Co., in which each 
commutator bar is connected to the bar directly opposite, is 
shown in Fig. 84; of the ten coils there given, 10 and 5 are in 
‘the neutral zone and are shortcircuited. 






9 S 


SON 






4 
U 


9) )Z 


3. MULTIPOLAR DRUM ARMATURES WITH SERIES WINDING. 


As no radical differences exist between series windings for 
ring and drum armatures, the same conditions apply to both. 
(See page 33 et seg.) Observing that 6 = 2 and z= 2s the 


general formula gives s = y5 + 1, and the number of coils 


‘ ; : . 8n ‘ 
shortcircuited by each brush simultaneously is 3? being the 


CLOSED—COIL WINDINGS. 





















































ee ee a) 
\\ \y \W\ WW} | NY 
OK MK KR 
OX KKK KKK 


+ = 
Fig, 86. 


72 —  . ARMATURE WINDINGS. 


ss. i 

























2 3 QS TRS. 4G ES 


t~ 


\ 
” 






+ 





CLOSED—COIL WINDINGS. 73 


number of commutator bars. Assuming n = 4, y = 6, s = 13, 
Figs. 85 and 86 give a scheme complying with these assump- 
tions and agreeing with the Andrews-Perry winding, shown in 
Fig. 40. This winding can be easily carried out on the surface 





Fig. 89. 


of the drum as the development shows. In order to increase 
the effective length of inductor the poles are given the shape 
shown in Fig. 86. 

If the rectangle A, A, B, 5, be eliminated, and the remain- 
ing parts drawn together, the scheme shown in Fig. 87 is 
obtained, which method is given by W. Fritschie.* The single 


* German patent, No. 45808. 


74 ARMATURE WINDINGS. 


inductors are laid on the surface of the drum without double 
- bending.* With a large number of poles the inductors have 
only a slight bend. 3 
This variation can also be introduced into the parallel 
winding scheme of Fig. 81. The general formula becomes 











12’ 9 W 
Vd 
CU th 
Fig. 90. 
especially valuable in the case of superimposed winding 
spaces. 4 
Let n = 4, 8=y5+1=10x 2+1= 21, y=10, and 
that inductors from two coils shall be superimposed on the cir- 
-cumference of the drum. In Fig. 88 the coils are laid out in 
their natural succession, 1 1’, 2 2’, 3 3’, etc., and connected to- 


* Krapfung. 


CLOSED—COIL WINDINGS. is 


gether according to the formula, ie., 1’ with 1+10=11, 
2’ with 2+10= 12, ete. The position of the coils and 
their connections are extremely unsymmetrical, and without a 
winding rule it would be very difficult to connect the coils 
properly. The coils 1 1’ to 5 5’ lie only on the inner sur- 














Fig. 91. 


face, and coils 6 6’ to 1616’ on both the inner and outer’ 
surface. 

The completed winding may be better represented. if the 
coils be indicated in succession, and distributed around the 
circumference as equally as possible. 

In Fig. 89 the following succession is observed: 1 1’, 5 5’, 
1111, 16 te) 18185 88, 9 0'° 19-19’, 17.1704 4" 18 to 
12, 22, 2b er, 10:10, 20 20’,.16 16,6 6.13 13,3 37 






\DIE LIBR, 
a OF THE se 


UNIVERSITY | 
OF go 






76 ARMATURE WINDINGS. 


_ With an even number of coils the brushes are 180° apart, as 
in a ring winding. In Fig. 90 a winding of this character is 


V£h 
7+ 1=16. 


This winding is only applicable where 5 is odd. If it be desired 


that only one coil be shortcircuited by each brush at the same 


shown, the assumption being » = 6, y = 5,8 = 5 









Re o 
VN ape 9 
\ Ss 


Fig. 92. 


time, it is necessary that the number of commutator segments 


3 OO 


n 2 0) 
be 3% and that those at an angle of degrees apart be 


connected together. Fig. 91 gives a scheme employing 9 coils 
and 18 segments with four poles. ‘The cross-connections are 
shown within the commutator, similar to the Mordey winding. 
In the given position 2 2’ is shortcircuited, 9 9’ having just 
passed that point, and 4 4’ is approaching it. 


CLOSED—COIL WINDINGS. TT 


A drum winding of Alioth & Co. shows that where 5 is 


even, a series winding can be obtained with an even number of 
coils, which winding is shown in Figs. 92 and 93, and agrees 
with the scheme of Fig. 54. The Alioth winding can be better 
understood from Fig. 93. The heavy lines show the front of 





Fig. 93. 


the armature and the connectors to the commutator. The 
developed scheme, Fig. 94, is interesting from the fact that it 
shows a mixture of loop and wave winding. 

Each element has four inductors (6 = 4) shown in Fig. 94 
by heavy lines. There are five elements altogether. The 
numbers Ja, [la, [1la, IVa, Va, denote the beginnings, and the 
ends are denoted by Je, L/e, IITe, IVe, Ve. 


78 ARMATURE WINDINGS. 


From the formula, y 


2/20.) 
= iz Bs 1) = 8. Therefore, Je is to 


be connected to Je, + 3 = IVa, and IVe with 1Ve, +3 =T 
— 5 + 2, therefore with Ja, etc. 


4. MULTIPOLAR ARMATURES WITH MIXED WINDINGS. 


The schemes given for ring armatures are easily applied to 
drums, and no new examples need be given. 


REMARKS UPON THE CONSTRUCTION OF DRUM ARMATURES. 


The practical construction of a winding, especially with 
a drum armature, differs considerably from the schemes given. 
It is therefore important to call attention to a few salient 
points. 





<> 

oS 
Vs 
asx 








YD WHOA WHA VBA WY 
aA 
eee 
AWA OH 
XLS 
7 : | iM : 
3 pees 
a Roa ae 


The methods used to wind the coils upon the armature may 
vary. Fig. 95 gives a commutator end view of a bipolar arma- 
ture. The number of coils is assumed to be 14; the number 


CLOSED—COIL WINDINGS. 79 


of winding spaces 28. Corresponding with the schemes in 
Figs. 60 and 61, the coils must cross the rear end on a chord 
of the circle. 

Beginning with the winding at a, the conductor is first 
taken to the point 6 on the front end, then carried along the 
surface of the drum to the back end, then carried. across along 





a chord, and brought forward again to the point ec. The opera- 
tion is repeated until the desired number of turns is obtained. 
In this figure each coil has only two turns. If 2—3—4—6, or 
more conductors of smaller sections be substituted for one of 
the large conductors previously considered, they may all be 
wound as one conductor or as several. 

If coil A be obtained in this manner, and taking each time 
alternate winding spaces, the coils B, C, D—O be wound, © 
when the last coil OQ is finished, all the winding spaces will be 
occupied ; and on joining together the free ends as specified, the 


80 ARMATURE WINDINGS. — 


fourteen points of connection to the commutator segments will 
be obtained. : 

If the number of winding spaces be equal to the number of 
coils, Fig. 67, the coils must be wound in successive spaces. 
When half the number of coils have been thus wound, all the 
winding spaces will be occupied, and the remainder of the coils 
must be wound over the first half, each two adjacent ends being 
joined to one commutator bar. 

If the connections to the commutator are to follow the 
schemes given in Figs. 62, 63, 68, 69, it is better not to bring 
out both ends, a and e, on the same side of the drum, but to 
start the winding at.d, then one-half of the projecting ends are 
bent to the right, and the rest to the left, and joined to the 
commutator according .to the scheme selected. 

A better arrangement of the mass of wires on the ends of the 
drum, and a winding of better appearance, can be obtained if, 
instead of the connections being invariably carried across to 
the right of the shaft they be divided between the two sides. 
This has the disadvantage, however, of taking up more room 
on the ends. With large conductors this becomes particularly 
noticeable, but may be obviated by the use of several smaller 
wires wound as a single conductor. 

For example, given a drum whose circumference is divided 
into 24 winding spaces in which 24 coils are to be wound, each 
coil to consist of two convolutions of four wires each whose 
diameter is about 1.5 mm. The connections are to be carried 
out according to the scheme given in Fig. 68. In Fig. 96, the 
position of the first four coils is given. These are wound in 
the succession I, IJ, HI, 1V. Beginning with 4 wires at a, they 
are carried to position 1, thence along the surface of the drum 
to the rear end, then across to the opposite winding space, and 
along the surface of the drum to 2; across the front end to 3; 
from here to the rear face again; ‘then across on the other side 
of the shaft to 4; and along the surface of the drum to the 
front end, which completes the first coil. After winding twelve 


GLOSED-COIL WINDINGS. 81 


coils in this manner twelve more are wound outside of them. 
One of these outside coils is shown in the figure, 1’ and 4’ 
being the ends. ‘The method of connecting the 24 coils with 
each other is obtained from Figs. 68 and 69. 

If the conditions given were, to wind twelve coils of two 
turns each, consisting of 8 wires wound as one conductor, the 
winding would have been carried out in the same manner. In 
this case the ends at a and 4’ are joined together and to a com- 





Fig. 96. 


mutator segment, also the ends at 4 and 1’. A symmetrical 
arrangement of the mass of wires and a winding of neat appear- 
ance can be obtained by using the method shown in Fig. 97 for 
a bipolar winding. The coils are wound in pairs, and two suc- 
cessive pairs are at an angle of 90°, or nearly 90°, with each 
other. It is assumed in this figure that the ends a and e of a 
coil are upon the same side of the drum as in Fig. 95. Begin- 
ning with the pair 1, observe that the ends a and e of the 
first coil lie upon one side of the drum and the ends a and e 


82 ARMATURE WINDINGS. 


of the second coil le upon the opposite side. The position of 
all the pairs of coils as indicated in the figure by I], HI, .. . 
VII, are obtained in the same manner. The shaft lies between 
the two coils of each pair. 

If there be 28 winding spaces, and the number of coils 
remains 28, it would become necessary, after having wound the 
first seven coils, to wind a second series of coils in the same 















































Cla d 
VW WV 
4% 
.° 33 
if x Mi 
) 6 
: ou 
SE = : I 
; (—) 
+) | o 7 
I \7 FT 
2: 2 
wy 3 3 ea 
W Haas Wl 
I 
ddb-b—alty 
Fig. 97. 


succession over the first, in such a manner that the ends of the 
coil wound over I, should be brought out at dd. 

If, however, it is the intention to use 14 coils, each occupy- 
ing two winding spaces, the first pair of the second set is wound 
‘over 1 in such a manner that the free ends, ae, ae, of both 
pairs coincide in position, for they are in this case connected 
in parallel. 

To properly connect these ends to the commutator, the begin- 
nings and ends of adjacent coils are connected to one bar. 


CLOSED-—COIL WINDINGS. 83 


In this winding it is preferable to substitute a conductor of 
several strands for a solid wire. 

To illustrate the difference of potential between successive 
coils, the coils in Figs. 95 and 97 are numbered from 1 to 7, 
starting at the negative brush, the numbers indicating approxi- 
mately the difference of potential between the coils. In the 
case where two coils cross at some point, the difference of 





Fig. 98. 


potential between the two crossing coils is proportional to the 
difference between the numbers which represent them. <A 
winding of this description is best arranged when the least 
difference of potential exists between coils which cross. : 

In Fig. 95 as well as 97,it is shown that the greatest differ- 
ence of potential exists between coils which cross; there being a 
cross between 1 and 7, 7 and 2, and between 6 and 1. These 
windings are therefore equivalent in this respect. 


84 ARMATURE WINDINGS. 


The exact position of the winding and the number of cross- 
ings cannot be previously determined. With careful work- 
manship both schemes, Figs. 95 and 97, will give good results. 
The same remarks which have been made upon bipolar arma- 
tures can also be applied to multipolar windings. ‘The coils 
may be wound in either manner with equally good results. 

To obtain a better and more permanent position for the 
wire, a number of pins, made either entirely of insulating mate- 
rial or of metal insulated from the winding, may be let into 





ends of the drum to act as points of support for the coil. Fig. 
98 represents a 4-pole winding with 12 coils. The succession 
in which the coils are wound is as follows: 
LY, 44, 1595 101050330 6,99 5.42 82 2 2',0.0, 
8 8’, 1111’; if the winding be carried out in this order, the 
coils will be symmetrical, the mass of wire on the ends of the 
drum will be well distributed and of neat appearance. 
The winding is begun at a (see coil 1 1’); carried across 
the front end embracing two insulated dividing pins qq, to b, 


CLOSED—COIL WINDINGS. 


then along the surface of 
the drum to the rear end, 
then again embracing two 
dividing pins to the second 
winding space of the coil, 
then carried along the sur- 
face of the drum to . 
This is repeated until the 
desired number of turns is 
obtained. Especial care 
should be taken in bring- 
ing out the ends a and e. 
If they be connected as 
shown in the figure, the 
points of connection to the 
commutator segments, A, 
B, C, are obtained. 

After the winding is 
completed, a disk having 
holes corresponding in po- 
sition with the retaining 
pins may be fastened over 
the winding, serving to 
secure the pins in their 
position. 

Alioth & Co. (see Fig. 
92) wind their armatures 
with “formed” coils, which 
were previously given a 
trapezoidal shape by being 
bent over a wooden form. 
Owing to their method of 
construction the insulation 
can be practically perfect. 

Differing radically 









































SS 


B 














85 


Fig. 700. 


86 ARMATURE WINDINGS. 


from the methods of winding described are those in which the 
connectors do not touch each other in crossing. The first 
winding of this description was introduced by the Siemens 
Company,* and used for arma- 
tures of low potentials with 
heavy currents. 

Fig. 99 shows one of these 
armatures. In this armature, 
copper rods of large cross- 
iw PTS ay section are used. These are 
| joined to the commutator, ac- 
cording to Fig. 62, by copper 


strips bent in such a manner 





ial fat 68 b as to lie in two parallel planes 
a7 ap igs At with air insulation between. 

ie a de Crompton and Swinburne + 
used this winding for machines of higher electromotive force, 
using flat copper bars laid edgewise on the drum, with the ends 
joined by copper strips bent spirally and lying in different. 
planes. The author uses this bar winding for : 
4-pole and other multipolar lighting generators using. f, 4 cI 
notched armatures. 

(This method of winding with copper bars and 
bent cross connectors has been used extensively in ] 
this country. — TRANSLATOR. ) a 

Figs. 100, 101, 102, show the winding of a 4-pole Fig. 102. 
armature. To prevent confusion, only 21 coils are shown, con- 
sisting of flat copper bars. There are in all 42 copper bars 
necessary, 21 having the length Z, and 21 the length J,. 
These are laid alternately around the periphery of the drum. 
Of the bars, those having the length LZ, are connected to the 
commutator. Around the surface of the drum there are 42 




















CI 


narrow slots into which the insulation and the copper bars are 


* Elektrot. Zeitschr., vol. 2, p.54; S. P. Thompson, Dy. Elect. Mach., p. 266. 
+ S. P. Thompson, Dy. Elect. Mach., 3d ed., p. 167. 


CLOSED—COIL WINDINGS. 87 


let. The cross connectors are made of sheet copper of the 
shape shown in Fig. 102, having two arms a and 8, and the 
lug ¢. These are bent on a form to the right shape, a ¢ 6, and 


(é 














TnI 























C222 











Q> 











TTT in no 
“A 
































Fig. 708. Fig. 104. 


the ends a and 6 each connected to a bar. The adjacent con- 
nectors-are separated by a piece of insulating material of the 
same form (or wrapped with 
silk tape and shellacked. — 
TrAns.). After all these con- 
nectors have been put in place, 
a ring of insulating materials 
is slipped over the projecting 
lugs ec, and fastened with a 
nut m. If the W. Fritsche 
winding given in Figs. 81, 
86, 88, be represented as on 
the surface of a drum, and 
each coil consist of only one 
turn, the winding can be car- 
ried out in the same manner as the Siemens method so that 
the connectors can cross each other without touching. 

Fig. 103 gives a side view, and Fig. 104 the section of a 
winding according to the scheme given in Fig. 88. The mutu- 
ally parallel bars 1, 2, 8, . . . . ete., are placed upon the cylin- 





Fig. 105. 


88 ARMATURE WINDINGS. 


der whose diameter is d, and the bars, 1’, 2’, 3’, which cross the 
other bars 1, 2, 3, are situated on the surface of a cylinder of 




































































































































































(tt i 
YG 
t ¥ ~ 

(et Tm) 
le —— S 

: as | 

ci es. i| 
(zc — 

AS 7 
<< — >) 

Fig. 106, 


larger diameter, D. The points of apparent intersection of the 
rods lying in the two planes are joined together, but are insu- 
lated from ‘the adjacent points of apparent intersection. Be- 

tween the two cylinders d and 


















































ae z ~  D sheets of insulating material 

(= = MEE On| are inserted. 
The idea of making use of 
the advantages of the Siemens 
' Dar winding for armatures 
whose coils must consist of 
le : : several turns, was carried out 
~ « J) practically by R. Eikmeyer.* 
dl fa no eke shaped wire coils, of Eik- 
Bi meyer, and the bar winding of 


Siemens, have the same form. 
Fig. 106 gives a side view of a bipolar drum having 36 coils of 
the previously mentioned form. Fig. 105 gives an end view 
of the same with the commutator removed. Fig. 107 gives a 
plan view of a single coil, A—B being the axis of the drum. 
The coils are all of the same shape. On one side of the axis 


* German Patent, 54413, Feb. 14, 1888, 


CLOSED—COIL WINDINGS. 89 


A—B, the coil is of less outside width than the inside width of 
the other half. This peculiarity of form is carried out regard- 
less of the number of turns in the coil, and of the changes in 
the shape of the core. 

In Fig. 107, 6—4, represent the part lying upon the surface 
of the drum, and c—e, the part lying on the face ; ¢,—c, are the 
windings, and d—d, the ends leading to the commutator. The 
side 6 of the coil is longer than the side 6,, so that when the 
coils are in position on the drum, the side 6, of each coil clears 
the side 6 of the other coils. On the circumference of the 
drum, the long and short sides alternate, and the pins a prevent 
the coils moving on the drum. The figure shows that the form 
of the connector across the face of the drum is a spiral, passing 
from the periphery of the drum toward the center, then along 
a line nearly parallel to the axis of the drum, and along another 
similar spiral to the opposite side of the drum. 

During this cycle the wires change their position, so that 
while on the surface of the drum they lie alongside each other, 
on the ends they are superimposed. This winding of Eik- 
meyer’s, and that of Alioth & Co., have the good feature of. 
equal lengths of wire, therefore equal resistance in the branch- 
ings of the circuit, and the additional feature that damaged 
coils can be readily replaced. 


DISK ARMATURE WINDINGS. 


The coils of Ring and Drum armatures turn about an axis 
which is perpendicular to the direction of the lines of force in 
the magnetic field. From this it follows that the plane of the 
coil is at one time parallel and at another time perpendicular 
to the direction of the lines of force. 

On account of this arrangement, the lines of force pass for 
a considerable distance through the armature core. The core 
is therefore made of iron, and for mechanical reasons, revolves 
with the inductors. This introduces a number of evils which 
in multipolar machines are especially noticeable. The repeated 


90 ARMATURE WINDINGS. 


magnetization and demagnetization of the core causes losses 
from eddy currents and hysteresis, which losses amount to seve- 
ral per cent in the best apparatus. Besides this, the heating of 
the core from these losses limits the allowable heating in the 
conductors and consequently the total output of the machine; 
and finally, the inducing coils, which are distributed in various 
parts of the magnetic flux, cause a cross-magnetization, which 
weakens and distorts the magnetic field. 

In disk armatures, the inductors move in a plane, perpen- 
dicular to the direction of the lines of force, about an axis par- 
allel to them. ‘The space which the inductors require in the 
magnetic field, in the direction of the lines of force, is limited 
to the thickness of the coils, and the iron core can be omitted, 
the lines of force passing from pole to pole directly through the 
armature windings. 

These features render it possible to make a disk armature 
of comparatively little weight, even when a large diameter is 
employed; it is therefore possible to obtain a high peripheral 
velocity with a low number of revolutions. Owing to the 
complete ventilation which may be obtained by this form of 
construction, it is possible to increase the current density in the 
armature, and hence increase the output of the machine. As 
no iron is used in the core, in order to produce an intense mag- 
netic field in the space between the poles in which the armature 
revolves without excessive magnetizing force, it is necessary 
that this space be made as short as possible. Therefore the 
coils, subject to induction, should occupy as small a space as 
possible in the direction of their axes. This requirement, as 
well as the connection of the inductors with each other and 
with the commutator, has prevented the more general adoption 
of this form of armature, and it is only within the last few 
years that their difficulties have been satisfactorily overcome. 

Disk armatures are generally used for multipolar, but may 
also be designed for bipolar machines. 

Series winding is especially applicable to multipolar disk 


CLOSED—COIL WINDINGS. 91 


armatures, as the desired E. M. F. can be obtained with few 
turns in each coil, and is also free from the difficulty which 
arises in multipolar armatures with parallel winding; that 
is, that the various branches are not all subject to exactly 
equal inductions, hence have unequal KE. M.F.’s induced in 
them. 

In the following pages several forms of disk armatures 
having only historical interest will be mentioned. The first 





Co 
HQ 
X\ AWS 


Fig, 108. 


considered is the disk armature of Niaudet.* This armature 
can be regarded as a Gramme ring armature, having the coils 
turned through an angle of 90°, so that all the coils lie ina 
plane perpendicular to the axis of rotation. The connections 
of the coils with each other and with the commutator remain 
the same, the beginning and the end of two adjacent coils 
leading to a common commutator bar. 

The magnetic field is obtained by the use of two horse-shoe 


* Kittler, Handbuch, Vol. ii., p. 23. 


92 ARMATURE WINDINGS. 


magnets, so arranged as to present the north pole of one to the 
south pole of the other, and vice versa. 

In Fig. 108, which is a diagrammatic representation of this 
armature, one of these horse-shoe magnets is considered as 
above the paper, the other below. If this armature be rotated 
through the magnetic field as shown, a reversal of current 














. et * 
oo-7- Zz 
ee 
sg a 
- . 
a S 
. 
s 
: ; 
7 
N 
¢ ~~ s rae 
¢ ed on 
»S . re ¢ 
‘ fe 1 bg 
esa ? a 
. ? - ~ 
pal . ¢ ° 
ee ‘ ae Ok 3 
a % als? 4 
‘ c Wy ; . ar gt 
. 
oy . \ ee Pid a Lge ys ‘ 
ia mae re . 4 . 
y aa +: es ‘ ‘ 
aaa Ps a 
~ ‘ .) 
¢ i . J 3 ) 
r os . Pat 
bs . 
Py - Eg sl feed By Z \ 
Ps . 
‘ . > - ae ” 
e ‘ 
N ‘ ' 
~TKLLAL SS S/S PPO twee ccee -_ 
: ’ 
-- ~ ai => . 
-se wee ‘ 
‘ s : 
- ‘ 
a = 
’ - oat 2 (a ) - 
% ~ = hepekS x ; 
e a ae ! 
~, se 
¢ 4a y 
F ae 3 4 eal. ~ 
‘ e 1 ‘ 
s 7 
\ 7 a . * 
¢ od ; 
. Z Se ' eee 
. Oe ah Kd wos v No sCN 
rf J ' > * 
¢ 
ae - . “ ‘ 
- sat 
? . ¢ 
s ‘ 
. s 
Pi ae ig . si 4 
N%es Zi ae 
. af 
. 
‘. 
* ‘ 
‘. . 
» P 
. 
te aE een Goad S 
° 
Fig. 109. 


takes place in each coil, when it is in such a position that one 
of its diameters coincides with the pole-line, WS. 

If the brushes be set so as to shortcircuit the coils that are 
in this position, the armature will be divided into two branch- 
ings, the current flowing in an opposite direction in each, and 
a direct current will flow in the exterior circuit. The same 
construction was also adopted by Wallace-Farmer, and Soren 
Hjorth. 


CLOSED—COIL WINDINGS. 93 


THE HOPKINSON-MUIRHEAD DISK ARMATURE.* (Fic. 109.) 


The connection of the coils with each other and to the 
commutator in this type of armature agrees with that of the 
Niaudet. A peculiar feature is, that the coils lie in two planes, 
the coils in one plane being advanced half the width of a coil 
beyond those in the other. : 

These coils are fastened to the sides of a core built up of 
strips of iron, and are held in position by radial bolts. The 
number of magnetic fields is equal to or less than one-half the 
number of coils, and they are otherwise arranged in the same 
manner as Niaudet’s. ! 

In the diagram, Fig. 109, the position of the coils in the 
plane lying to the rear is shown by dotted lines. 


SIEMENS & HALSKE DISK ARMATURE.?+ 


VON HEFNER-ALTENECK DESIGN. 


A very ingenious method of constructing a multipolar disk 
armature, with a series winding, was designed by Von Hefner- 
Alteneck ; in this winding, only one coil is shortcircuited at a 
time by each brush, the same as in bipolar machines. The 
successive magnetic fields are of alternate polarity. The num- 
ber of coils in the armature is less than the number of fields, 
in fact, s = (n — 2). 

In Fig. 110, 6 coils are represented, rotating between 8 
magnetic fields. Of these 6 coils, but two opposite coils are 
wholly in a magnetic field, the others being at a greater or less 
distance from a field. The rotation of the armature, therefore, 
does not produce a maximum induction in all the coils at the 
same time, but in successive coils in successive parts of the revo- 
lution. 

Considering the armature at any part of a revolution, it is 


* English patent, 4886, of 1880. ; 
+ German patent, 15389. 1881. Kittler, Handbuch, Vol. ii., p. 29. 


94 ARMATURE WINDINGS. 


evident that it may be divided into two halves, by a line 
passing through its axis, such that the direction of the flow of 
the currents in the halves is opposite, while the impulses are 
additive. This division line continually changes its position 
during the rotation of the armature, but always intersects the 
points of the circuit formed by the coils which are connected to 








Fig. 110. 


the particular commutator segments upon which the brushes 
rest. The commutator consists of 


3 n 
C= 3 x s segments, 


2 x 860 
degrees 





n ; 
and every 3 segments which are at an angle of 


apart, are connected together, and are also connected to the 
connectors of two adjacent coils. In the Fig. the commutator 


has 24 bars, and 5 = 4 segments belong to each group. The 


connection of the segments in each group (for example, 1,1,1,1, 


CLOSED—COIL WINDINGS. 95 


2, 2, 2, 2,) to each other and to the windings is accomplished by 
means of insulated rings carried by the shaft. If the successive 
segments of the 6 groups be numbered from 1. . . 6, and the 
corresponding connecting wires between the coils be also num- 
bered 1 . . . 6, then the shortcircuited coils will be those which 
are included between the points on the connecting wires, whose 
numbers correspond to the numbers of the commutator seg- 


. 
| 


Fig. 111. 


ments on which the brushes rest; for example, if one brush 
rest on segments 5 and 6, and the other upon 2 and 3, the coils 
lying between the connection wires 5 and 6 are shortcircuited, 
likewise those between 2 and 3. 

Instead of having more magnetic fields than coils the number 
may be less, and need not be exactly two less. The number of 
coils may be increased, for example, to double the number. 
The coils may be located in two planes, as in Fig. 109, for the 


96 ARMATURE WINDINGS. 


Hopkinson-Muirhead disk armatures, not necessarily with the 
centers of the coils in one plane midway between the centers 
of the coils in the other. Fig. 111 shows the inter-connections 
of the coils for a machine with eight fields and twelve coils. 
The coils which are subject to the induction of the field succes- 
sively are not connected successively, but at regular intervals, 
as shown in ‘the diagram, and are correspondingly cut into 
circuit. The number of commutator sections with this scheme 
is 48, arranged in 12 groups of 4 segments each. 
































Fig. 112. 


The disk armatures which have been described have no prac- 
tical importance. By application of the schemes developed for 
ring and drum armatures, practical direct-current disk arma- 
tures may be evolved. In conclusion, Faraday’s disk may be 
mentioned. -This well-known apparatus is illustrated in Fig. 
112, which shows a copper disk rotated in a magnetic field in 
such a manner that lines of force are continually cut by the 
disk, and by means of brushes bearing on the axis and periphery 
of the disk an uninterrupted current is obtained in the exterior 
circuit. 


CLOSED—COIL WINDINGS. 97 


DISK ARMATURES OF W. THOMSON * AND POLESCHKO.t 


If the copper disk (of Faraday) be slit into radial arms 
fastened to a common axis, but insulated from each other 
toward the periphery, and if this disk be rotated in magnetic 
fields of opposite sign as in Fig. 113, Poleschko’s arrangement | 
will be obtained. It is assumed that there is above the plane 
of the figure a north pole opposite to the south pole, and a 












Q 


ty Lr 


pL LLL Lea 







XY 








L 


Fig. 113. 


south pole opposite the north pole. The brushes bear on 
the periphery of the disk on a line with the poles (S. W.), 
and as the E. M. F.’s induced in the arms of the disk on which 
the brushes rest are additive, the E.M.F. obtained will be 
double that of a Faraday disk. The radial slitting of the disk 
prevents wasteful eddy currents. W. Thomson joins the outer 
ends of the radial arms with copper strips, and insulates the 


* S. P. Thompson, Dyn. Mach. Third ed., p. 233. 
+ La Lum. Elec. Vol. xxxv., 1889, p. 610. 


98 ARMATURE WINDINGS. 


inner ends which are joined to the segments of an ordinary 
commutator with two brushes. 

These are open-coil armatures, and are mentioned here as 
they illustrate the origin of disk armatures. 


PACINOTTY’S DISK ARMATURE.* 


In 1881 a machine was shown at the Paris Exposition 
which had been invented by Pacinotti in 1875. His armature 
also consisted of radial arms rotating between magnetic poles of 
































es 
0 
| 
¢ 
B’ o | B 
“t: 3 go = Ox i m! 
ANH : 
rs y 
4 
CATAL LAI (VO 
Fig. 114. 


opposite sign, but the arms were connected so as to constitute 
a closed winding. ‘This method of construction is given in 
Fig. 114. The surface of the poles is very much increased in 
comparison with those shown in Fig. 113, so that in all the con- 
ductors in one-half of the armature the current flows radially 


* S. P. Thompson, Dyn. Mach., p. 206. 


CLOSED—COIL WINDINGS. 99 


inward, and in the other half radially outward. The manner 
of connecting the conductors follows the general rule, here as 
well as in the Pacinotti Ring armature. 

In the scheme given, s = 10, y¥ =s +1 = 11, therefore 1 
must be connected to 1 + 11 = 12 or 2. The commutator 
segments are shown on the periphery for the sake of clearness. 
The circuit is as follows; from the brush B, through the exterior 
circuit to B, into the armature, where it divides itself as follows: 

Bye, 10, AG ea as oy 2 8, OG Bs 
B.,'8',.8,.0,1, 0; Goo ,.0, 4, 4; B. 


EDISON’S DISK ARMATURE. 


In 1881 Edison patented a machine in which the armature 
is nearly the same as that of Pacinotti. 

















Fig. 115. 


By transferring the commutator connections from the con- 
nections of the radial arms which lie on the periphery, to 


ARMATURE WINDINGS. 


100 





those which are in the inner part of the disk, Edison’s scheme, 


struction of this 


The actual con 


shown in Fig. 115, results. 


Fig. 116 and in section in 


plan in 


arrangement is shown in 


Fig. 117. 


The sixteen radial conductors consist of copper strips 


e€c- 


.) well insulated from one another. Their conn 


C0, @ a2 


cS 
. 


jaa) 














WIA 
Oe 


RW 











CO 
XX >’'’WwY 











a 
So 


x 


CLOSED—COIL WINDINGS. 101 


tion with each other on the periphery is effected by eight con- 
centric copper bands insulated from each other. The disk is 
mounted on a wooden hub, and the radial arms are connected 
to the commutator by means of eight insulated copper rings 
carried by this hub. ‘The development of both these schemes 
is shown in Fig. 118. : : 

A comparison of this with Fig. 71 shows the identity of the 
scheme of connecting with the Von Hefner-Alteneck drum 
winding. If the development.of the scheme given in Fig. 118 
be made circular, so that the side AA forms the outer circle, 
Pacinotti’s scheme results; if this side be made the inner circle, 
Edison’s scheme is obtained. 

















Fig. 1719. 


EDISON’S * MULTIPOLAR DISK ARMATURE WITH PARALLEL 
WINDING. 


Fig. 119 shows the scheme of connection given in Fig. 115, 
extended to cover a multipolar field. This is identical with 
the drum armature winding shown in Fig. 75. 


* The Electrician, December, 1889. 


102 ARMATURE WINDINGS. 


APPLICATION OF THE ANDREWS-PERRY WINDING TO DISK 
ARMATURES. 


A new group of disk armature windings may be arranged 
by applying the Andrews-Perry winding for ring armatures to 
disk armatures. 

The most simple form in which this may be done is to 
change to a circular form the scheme given in Fig. 86 for 
drum armatures in such a manner that the parallel conductors 


ga, 





Fig. 120. 


1... 18 and 1’... 13’ become radii. Fig. 120 shows a 
scheme developed in this manner, designed for eight poles. 
According to the formula, the number of inductors must be 


ee o(ys + a) . Forseries connectiona=1. In Fig. 120, 6 = 2, 


y = 5, therefore z= 2(4x5+4+1)=42=%s8. Every two 
inductors are joined in one pair, forming one coil, indicated by 
the same numbers. 1’ is to be joined to 1 + 5 = 6, 2’ with 7, 


CLOSED—COIL WINDINGS. 103 


3’ with 8, etc. The number of commutator segments is 21. 
There are 5= 4 coils shorteircuited by each brush at the same 


time, and for the position of the armature shown in the 
drawing, the coils shortcircuited by the negative brush are 
[21, 21’] [50°] [19, 10’] [15, 15°], and by the positive brush 
[18’, 18] [13’, 13][8’, 8] and [3’, 3]. The shape of the pole 
piece is determined by the shape of the coil. To prevent 
opposing E. M. F.’s, the poles must be cut off at an angle on 
the outside, and the edges made radial. 

The practical construction of a disk armature according to 
this scheme presents many difficulties, which have been over- 
come in various ways. 

The first method to be considered is a disk armature with 
an oblique winding. ‘The over-lapping coils in this armature 
stand at an angle to the plane of rotation. The angular width 





Piss ae F ee 


GG 


Fig. 121. 


is such that when one side of the coil is 
in one magnetic field, the other side lies 
in a field of opposite sign. Fig. 121 
gives the position of the coils relative to 
the magnetic field. The development 
shown gives a view of the circumference 





7 a 
Fig, 122, 


of the armature. 

The shape of a single coil for 8 poles is shown in Fig. 122. 
The ends of the coils can be joined, according to Fig. 120, 
for high E.M.F.’s, or as in Fig. 77, in parallel for low 
E. M. F.’s. 


Windings employing oblique coils have been devised 


eR” oF THE ep 


LINIVERSITY 


104 ARMATURE WINDINGS. 


by Ayrton and Perry,* by Elphinstone-Vincent * and _ by 
Desroziers.| The method of connection employed is not 
known to the author. If each coil consist of one turn, and the 
entire winding be arranged on a thin disk in an oblique position 
and connected according to the general formula, the scheme 
given in Fig. 123 will result. This represents a development of 


CY ee a Raeaee LSZ 
»_— 
— J 12" fhe oS 


- 
~ ~. = 






- S 
~ . “. . 


- Ss . S s . 
~~ - ~ ~ ~ - 


ae mea = = = = “8 PS 5 OD eee ea: eee 
= VIBHA * WIA a 


Fig. 128. 

















the circumference of the armature. The radial inductors are 
shown as points, the cross connectors on the circumference as 
full lines, the interior connectors as dotted lines. The winding 
is carried out as follows: From 1’ along the inner surface to 
11, then radially outward, then from 11 obliquely across the 
exterior surface to 11’, then radially inward, and from 11’ on 
the inner surface obliquely to 21 and continuing to 21’, 10, 
10’, 20, 20’, 9, etc., returning to 1’. No crossing takes place, 
and the position of the brushes is given in the diagram. 


DESROZIERS’ DISK ARMATURE. t 


Desroziers’ method of winding disk armatures agrees with 
the scheme given in Fig. 121, whichis a wave winding, except 
that he employs a greater number of commutator bars than is 
there given. This he did with drum armatures, as shown in 
Fig. 91, and with ring armatures, as shown in Fig. 50, so that 
a brush shortcircuits but one coil, that is, one element, at a 
time. In this armature the number of radial inductors is 

* S. P. Thompson, Dyn. Mach., 3d ed., p. 206, 
+ La Lum. Elece., Vol. xxiv., 1887, p. 293. 


+ Elektrotechnic. Zeitsch., Vol. x., 1889, p. 200. La Lum. Elec., Vol. xxiv., 7 May, 1887, 
p. 294. 


CLOSED—COIL WINDINGS. 105 


2=b (v’ th 1), The number of commutator seoments, c= 25 : 


and every 5 segments lying at an angle of a degrees apart 


are connected together. Desroziers makes 5 odd in his ma- 


chines, — actually n = 6. The number of inductors, z, is always 
divisible by 4, and every four inductors with their connectors 











Fig. 124, 


constitute an element. In this manner the number of commu- 
tator segments is reduced one-half. ¢ = i x 5 = - In Fig. 
124 Desroziers’ winding is represented assuming n = 6, 2 = 2 
(8X5 +1) = 32, y = 5, ande = 24. This winding con- 
sists of straight radial conductors which are moved in the 
magnetic field, and are joined together on the exterior and the 
interior of the disk by spirally bent wires. Crossings of 


the connectors are entirely avoided by this method. A coil, 


106 ARMATURE WINDINGS. 


as considered in the formula, consists of two radial parts (6 = 2) 
and two connecting parts; for example, a a, 6, be. 

An element, according to Desroziers, consists of four radial 
parts and four connecting pieces, for example, aa, b, bee, d, de. 


From the junction of two elements, connections are carried to 


three segments, at an angle of ad tie = 120°. 


The complete scheme obtained in this manner is shown in 
Fig. 125. To prevent crossings (in the diagram) the dotted 


' 
: ' 
aa — 





Fig. 125. 


parts of the inductors are supposed to lie on the rear face of the 
disk, and the parts shown by full lines lie on the front face. 
The necessary rigidity is given to the armature by a wheel-like 
supporting disk made of German silver 2 mm. thick, which is 
fastened by means of boits to a hub on the shaft of the machine, 
and insulated on both sides with sheets of papier-maché fastened 
to the disk with pins. One-half. of the armature winding is 
fastened outside of each papier-maché disk before it is put in 
place on the German silver disk, so that two workmen can be em- 


CLOSED-—COIL WINDINGS. 107 


ployed on a winding, working independently of each other. 
After the complete halves of the winding have been put in 
position on the supporting disk, the proper connections are 
made between the windings and the commutator. 





Fig. 126. 


FANTA’S DISK ARMATURE.* 


Fanta’s method of construction requires that the parts of the 
armature subject to induction be made as thin. as_ possible. 
Owing to this fact he obtains an intense field with a small 
magnetizing force. 

The armature consists of a metallic supporting disk, #, in 
Fig. 127, having an insulating disk on each side. These insu- 
lating disks are each divided into 3 
concentric parts, A,B,C, of which the 
middle one (6) can be removed after pz 
the armature has been wound. ‘The 
other two remain permanently fastened 
in position to the supporting disk R. 
Before fastening the insulating disks to the core they are 
wound with wire. The plan of winding, which is illustrated 
in Figs. 128 and 129, is similar to that of Desroziers’. The 
path of the element on the core is as follows: starting from a, 
it passes along the rear side to the hole 4; passing through 
this hole, it follows an eccentric curve from e¢ to d; passes 






Fig. 127. 


* German Patent, No. 46240, March 25, 1888. 


108 ARMATURE WINDINGS. 


through the disk A again, and on the other side is carried 
radially from e to f. At f it passes through the ring (, 
follows the eccentric curve g, h on the front side of the disk; 
at h again through a hole to z, and is then brought out radi- 














Fig. 128. 


ally tok. An element of this winding is shown in Fig. 129. 
On each of the side plates, ABC A,B,C, a certain number 
of these elements are wound. The parts of the winding 
which are radial in their direction are all 
ee on one side of the disk, lying closely along- 
ae side of each other. ‘This side of the wound . 
disks is placed next to the supporting disk, 
and the rings AA, and CC, are fastened to 
ef it. The central rings, B and B, may be 
5 taken away, which allows the air gap to be 
ees materially reduced. ‘The elements are con- 
nected to each other according to the results desired, either in 
series or in parallel. 








CLOSED—COIL WINDINGS. 109 


JEHL AND RUPP DISK ARMATURES.* 


One of the greatest improvements in disk armatures was 
made by F. Jehl, who in 1887 patented a method of construct- 
ing disk armatures. 

It is a well-known fact that the cross connections on the 
rear face of a drum armature, can be so arranged as to avoid 
crossings. In Desroziers’ and Fanta’s winding the method by 
which crossings are obviated, is to build up the windings in two 

















/ 





Fig. 130. 


separate planes. This is the case in the Jehl and Rupp arma- 
ture, the halves of the armature being in two parallel planes. 

Here the elements do not require any support, being so 
shaped and proportioned as to give the necessary rigidity. The 
elements for parallel winding are bent to shape from blanks of 
the form shown in Fig. 130; and it may be seen from Fig. 131, 
that the elements a, and 4, lie in different planes. The left end 
a, is connected to the right end 6, of the preceding element, and 
the right end, 6,, to the left end, a,, of the succeeding element. 

If all the elements be joined, as shown, a closed circuit 
winding is obtained, one-half on each side of the armature. 

* German Patent, 43298; Kittler, Handb., Vol. ii., p. 39. 


110 | ARMATURE WINDINGS. 


_ The scheme of this winding is shown in Fig. 132, and it will 
be readily seen that it is a loop winding. For the sake of 
clearness a winding with a small number of coils has been 
selected. The parts of the winding a,),,a,b,,a,6,, etc., belong 
each to one bent strip. ‘The conductors lying upon the front 
of the armature are shown by heavy lines. 

In order to obtain the greatest number of coils in an arma- 
ture, the inner parts of the coils can be replaced by a thinner 


eee 


ad 
44 





Fig. 132. 


metallic band which must be increased in width to retain the 
original cross-section. With this change the coils may be 
brought closer together. 

The number of commutator segments can be equal to half 
the number of inductors, or several inductors of a group 
may be joined together, and the ends brought to the commu- 
tator. 

If the number of inductors z = 6 (y, +1), and they be 


CLOSED—COIL WINDINGS. 111 


joined together according to the general rule, a wave winding 
is obtained. In Fig. 183, 2=14, y=3,n=4. If connected, as 
shown, the number of elements will be 7. 

Jehl and Rupp also connect the winding as shown in 


Fig. 134. Here b =4,2=4(y% £1) or2 =4(3 x 2-1) = 20, 
y = 38. Each element consists of four radial arms, the begin- 


nings of which are numbered 1, 2, 3, etc., the ends 1’, 2’, 3’, etc. 
1’ is joined to 1 + y = 4, ete. 





Fig. 133. 


In the same manner as in the ring armature shown in Fig. 
52, the number of commutator bars may be reduced one-half, 
but if a commutator bar be inserted diametrically opposite each 


of the present bars the number will again become 5 . 
A difference which exists between the disk armatures of 


Desroziers and Fanta and that of Jehl and Rupp is that in the 
first the radial inductors belonging to one coil are in different 


112 ARMATURE WINDINGS. 


magnetic fields and are both active, while in the latter only one 
side of a coil is active. The width of the coil is somewhat 
ereater than that of the pole-piece. If the width of the coil 
were the same as that of the field, the neutral space would 





Fig. 134. 


disappear; it is therefore imperative that the coils be wider. 
The construction of armature coils from metallic strips lying in 
two planes may be advantageously employed in other windings. 


W. FRITSCHE’S DISK ARMATURE.* 


To W. Fritsche belongs the credit of having united the 
Jehl and Rupp construction with the Andrews,+ Perry and 
Desroziers windings, and of having evolved a practical method 
of carrying it out. The fundamental difference between Frit- 
sche’s disk armature and those of Desroziers and Jehl is that 


* German patent, No. 45808, June 19, 1887. 
+t Kittler, Handb., Vol. i., Stuttgart, 1886, p. 532. 


CLOSED—COIL WINDINGS. 113 


Fritsche used straight rods bent to lie in two planes. The con- 
nection is according to the general rule. Fritsche’s winding is 


given in Fig. 135, where n = 8, z= 42, 5 = 21 (elements) y = 5. 


Inductor 1 is to be connected to 1+y=6. The angle 
between 1 and 6 is bisected by the line OM. This inter- 
cepts the circumference of the interior limit of the winding 
at a. 1a and 6a show the positions of the inductors. The 
Fritsche winding may be derived from that given in Fig. 120 





Fig. 135. 


by substituting a triangular shape for the polygonal one there 
given, and by shaping of the pole shoes so as.to prevent oppos- 
ing E.M.F.’s being generated in the inductors. The same 
winding would be obtained if the scheme given in 87 were 
developed circularly. A comparison of the Fritsche disk arma- 
ture with the ring armature of Andrews, Fig. 49, will show 
that if in the latter figure, 1 and 1’, 2 and 2’, etc., coincide, the 


114 ARMATURE WINDINGS. | 


cross connectors themselves will give a correct scheme for a 
Fritsche disk armature, when n = 6, 2 = 82,y = 5. Fora col- 
lector, Fritsche uses the connection pieces at the junctions 
of the elements on the circumference. The position of the 
brushes on the circumference of the armature is shown in 
the figure. ‘The inductors themselves are made of bent sheet 
iron, the inner and outer ends soldered to the connection 
pieces ; the entire system of inductors is fastened to the shaft. 


OPEN-—COIL WINDINGS. emer 31, 


B. OPEN-COIL WINDINGS. 


Open-coil windings, whose elements were spoken of on page 
T, have become prominent through the Brush and Thomson- 
Houston machines. Their peculiarities and their methods of 
operation will not be entered upon here. They have been fully 
discussed in §. P. Thompson’s book, and also in Professor E. 
Kittler’s. The principle of the windings will be shown in the 
following pages. 


1. RING ARMATURE WINDINGS. 
BRUSH RING ARMATURE. (Fie. 136.) 


There are in all, 8 coils wound in the same direction. The 
rear ends of two diametrically opposite coils are connected 
together, that is, 1 to 1, 2 to 2, 3 to 3, 4 to 4; these connec- 
tions are indicated by dotted lines. The front ends of these 
pairs of coils are connected to the commutator. The commu- 
tator consists of four rings lying alongside of each other on the 
shaft, each ring consisting of two segments, each segment em- 
bracing 2 of the circumference. In the figure these rings are 
shown as lyingin the plane of the paper, and therefore of dif- 
ferent diameters. In the two inner rings, having the common 
brushes P, P,, the corresponding sections are shifted 90°, and 
are connected to the pairs of coils 1—1, 3-3, which also lie at 
right angles to each other. The outer rings with the common 
brushes, @, and @,, are connected to the remaining coils, 2—2 
and 4-4, and the segments are at an angle of 45° with the 
first pair. 

In the position shown in the drawing, and with the given 


116 ARMATURE WINDINGS. 


direction of rotation, the E. M. F. in 1-1 has attained its maxi- 
mum, that in 4—4 is increasing, that in 2—2 is decreasing, while 
3—3 lies in the neutral space. The current enters the armature 
at P,, passes through the coils 1-1 to the brush P,, thence to 
the brush ,, then to the coils 2-2 and 4—4, which are in parallel, 
to @,, and returns to P,, through the external circuit. The coils 
3-3 are cut out entirely. If the coils change position, a cor- 
responding change takes place in the path of the current through 
































them. Each coil is cut out of circuit twice for } of a revolution, 
and at that time when its E. M. F. is approaching or receding 
from 0. Those coils which are either approaching or receding 
fromthe point of maximum induction, are always in parallel. 
The number of coils may be increased if desired, still 
adhering to the Brush winding. Each pair of coils requires a col- 
lector ring, and every four coils lying at an angle of 90° require 
a common pair of brushes. These are connected successively in 
series. The armature of the largest Brush machine has but 12 


OPEN—COIL WINDINGS. 117 


coils. Fig. 137 shows its arrangement. While the armature 
is in the position shown in the figure, the coils 4-4 are in the 
neutral zone and are cut out of the circuit. The path of the 
current through the armature is as follows: 


Pola G UP eo Ge Pe > 


through the external circuit back to P,. 











rit : ay 














\ 
ry 








eau 





LZ AS, 
































Fig. 137. 


2. DRUM ARMATURES, THOMSON-HOUSTON WINDING. 


This armature is shown in Figs. 138-141. The core is com- 
posed of iron wire wound on two cast-iron supporting spiders, 
the whole forming an oblate spheroid. Pins are inserted in the 
edges of the cast-iron spiders for the purpose of properly spa- 
cing and guiding the three coils, which are wound on the core 
at an angle of 120°. 

The coils are wound in as follow: first, half of the first 
coil, then half of the second coil, then all of the third coil, then 


118 ARMATURE WINDINGS. 


the other half of the second, and finally the remaining half of 
the first coil. This method of procedure gives an equal length 
‘of wire in each coil, and the mean distance of the coils from the 
poles is the same. The beginnings of each of the three coils 
are connected together, and the ends are connected to the three- 
part commutator. The armature when completely wound is 
nearly spherical. The developed scheme shown in Fig. 138 
represents this winding. The starting ends a,, 6,, ¢,, are con- 




















ANAANNANANAAAANSARANSANARRARA § 


.A.)pJg.\ 





Fig. 138. 


nected together, and the ends 1, 2, 3 are connected to the seg- 
ments a, 6, ¢. Coil number 2 is in the neutral position in the 
figure, and is cut out of the circuit. 

The position of the coils relative to the commutator and to 
the brushes is shown in Fig. 139. The coils 1, 2, 8, are indi- 
cated by radial lines drawn from the segments a, 6, c, of the 


OPEN—COIL WINDINGS. 


commutator to the center; WV. S. is the pole line. 


HY 


If the arma- 


ture be revolved through 30° from the position shown, number 
1 will be in the position of maximum induction, number 2 





Fig. 





740, 


approaching this position, and number 3 will be in the neutral 


position. (See Fig. 140.) 


Coils 2 and 3 are connected in parallel, by the brush resting 
upon both 6 and ec. On revolving the armature further, number 
3 is cut out of circuit, and number 2 takes its place. ‘The time 


during which two coils 
are in parallel is there- 
fore very short. To in- 
crease this time, and to 
more advantageously 
employ the full field flux, 
the commutator seg- 
ments might be length- 
ned so as to overlap, as 
in the Brush machine. 
Thomson-Houstonattain 
the same end by using 





Fig. 141. 


a second pair of brushes set at an angle of 60° with the first 


pair, and connected to them, as shown in Fig. 141. 


120 ARMATURE WINDINGS. ~ 


3- DISK ARMATURE WINDINGS, WILDE’S DISK ARMATURE. 


In 1867 H. Wilde patented an alternating dynamo, the 
armature of which was so connected as to allow a part of the 
current to be rectified to excite the field magnets; in Fig. 142 
an arrangement of this same character is shown. 

An armature with eight coils revolves in eight magnetic 
fields of alternate sign. The coils in the armature are con- 





Fig. 142, 


nected so that a reversal of current takes place in all of them 
simultaneously. The commutator is shown in the figure as two 
interlocking tooth disks; actually they consist of two toothed 
cylinders mounted on the shaft. Each cylinder has as many 
projections as there are fields. One of these cylinders is con- 
nected to the beginning of the winding, the other to the end. 

A unidirectional pulsating current will be obtained if two 
brushes be used on adjacent segments of the rectifier. 

The coils may also be arranged in parallel, by connecting 
the beginning and the end of each coil with the rectifier. 


OPEN—COIL WINDINGS. 


FERRANTI-THOMSON DISK ARMATURE. 


In this case, as.in the previous one, the field magnets 


arranged circularly, and of alternate polarity. The armature 


121 


are 


consists of copper strips bent into a wave-like shape; the num- 


ber of layers is optional. 
143, but two layers are shown. 


In the diagram of this winding, Fig. 
The distance between the 


radial parts of the coils is the same as the distance between the 


centers of the fields. 





SSS SS 






LIKL2 
LE IKLI KR? 
LEE 
oa, 


LZ, SR 7Z2 
MLE ZZLaN 


CZZD 
CLL 










aziz LiLo 
LLL LAA ppp Oo 
QLLLLLL Af, 



















WADA Bwsay, 


SX 
SQ ss 


SS 
SS 


ie 
¢ 
a 


Fig. 143. 


strip are additive, and the total E. M. F. can be made available 
at the ends of a break made between any two adjacent coils of 
the winding. 

When the coils are in the position shown in the drawing, 
they are in the position of maximum induction. By connecting 
the armature coils in the same manner as is shown in Fig. 142 


a rectified current may be obtained, Instead of brushes, Fer- 
ranti uses grooved metal disks.* 


* Kittler, Handbuch, Vol. ii., p. 136. 


The E. M. F.’s induced in the copper 


189 ARMATURE WINDINGS 


BOLLMAN DISK ARMATURE.* 


The Bollman winding resembles that of Ferranti-Thomson, 
the difference being that in the Bollman armature there are sey- 
eral circuits, and the coils of the various circuits overlap. If 
a single circuit be taken from the armature it will be found 
to agree with the Ferranti-Thomson winding. The scheme of 





Fig. 144, 


Bollman’s winding is shown in Fig. 144, in which there are 
twelve magnetic fields arranged in a circle and of alternate 
polarity. There are altogether 24 armature coils, divided into 
four circuits of 6 coils each. The coils are built up of copper 
strip, and no iron is used in the construction of the armature. 
Each coil contains several turns, two turns being shown in 
the diagram, which consist of radial strips, and are con- 
nected at the ends by short circular pieces in such a man- 
ner that air may circulate through the winding. The coils 


* German patent, 35186, Nov. 18, 1884, Kittler, Handbuch, Vol. ii., p. 37. 


OPEN-—COIL WINDINGS. 123 


are all connected in series. The angular distance between 
coils is equal to that between the poles, therefore each coil is 
in two fields at the same time. 

In the drawing only one circuit is shown, a second being 
partially indicated by dotted lines. In order that the air-gap 
may be as small as possible, the radial strips lie in one plane. 
The connecting strips do not lie in the same plane as the radial 
strips, but are bent out to one side to prevent crossings, as 
shown in perspective in Fig. 145. In that figure a,, ¢,k, o,n, 
f,e are the radial inductors, and bede, fghi, klmn are the con- 
necting strips. The corresponding position of the other circuit 
is shown by the line pg. The connecting strips of two of the 

















2 
. ~~ 3 shat nar ay Ma ge 
ee ed 
Fig. 145. Fig. 146. 


circuits are bent to the right, and of the other two to the left. 
The collector is identical with the rectifier used by Wilde, but 
with the separate parts multiplied to cover the increased num- 
ber of armature circuits (in this case 4 times), having in all 
2s = 48 segments. The two ends of each circuit are con- 


nected to each 5 = 6 segments. The segments for the arma- 


ture circuits are represented in Fig. 144. The end, @,, is 
connected to the shaded segments, and e, to the others. The 


distanee between two segments of one circuit = : as 75a of the 


circumference. In Fig. 146 a developed view of the collector 
is given, which shows that the segments lie in a position 


124 ARMATURE WINDINGS. 


oblique to the axis, so the brushes must rest on at least two, 
and at times three segments. 

Thus, of the armature coils, at least two, and sometimes 
three, are in cireuit. There is always at least one coil that is 
cut out, and at the time when its E. M. F. is zero, and about to 
reverse. The + and — signs of Fig. 146 refer to the points 
between which the direction of the current in the armature cir- 
cuits reverses, hence the brushes may be either 1—38—5—7—9 
or 11 twelfths of the circumference apart. 





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ELECTRICAL SCIENCE. 


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ABBOTT, A. V. The Electrical Transmission of Energy. A Manual for the 
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ARNOLD, E. Armature Windings of Direct Current Dynamos. Extension and 
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ATKINSON, PHILIP. Elements of Static Electricity, with full description of the 
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